Remove support for PacketBufferTLVReader using chained buffers.

[bzbarsky-apple]

It was unused, and if we can guarantee a contiguous buffer consumers can be safer

Problem

Reading from a TLVPacketBufferBackingStore is probably broken in practice for reasons similar to those described in #9575. And we have people doing unsafe things involving GetLength with TLV readers initialized with packet buffers.

Change overview

Drop the likely-broken and unused support for chained buffers in PacketBufferTLVReader and expose safer span-getting methods on it.

Testing

Existing unit tests modified accordingly.

[github-actions]

Size increase report for "gn_qpg-example-build" from 5d2654a

File	Section	File	VM
chip-qpg6100-lighting-example.out	.text	16	16

Full report output

BLOAT REPORT

Files found only in the build output:
    report.csv

Comparing ./master_artifact/chip-qpg6100-lighting-example.out.map and ./pull_artifact/chip-qpg6100-lighting-example.out.map:

BLOAT EXECUTION FAILED WITH CODE 1:
bloaty: unknown file type for file './pull_artifact/chip-qpg6100-lighting-example.out.map'

Comparing ./master_artifact/chip-qpg6100-lighting-example.out and ./pull_artifact/chip-qpg6100-lighting-example.out:

sections,vmsize,filesize
.debug_info,0,479
.debug_str,0,44
.symtab,0,32
.text,16,16
.debug_abbrev,0,10
.strtab,0,7
.shstrtab,0,1
[Unmapped],0,-16
.debug_aranges,0,-24
.debug_frame,0,-120
.debug_ranges,0,-288
.debug_line,0,-471
.debug_loc,0,-766

[github-actions]

Size increase report for "nrfconnect-example-build" from 5d2654a

File	Section	File	VM
chip-lock.elf	text	4	4
chip-lock.elf	device_handles	-4	-4

Full report output

BLOAT REPORT

Files found only in the build output:
    report.csv

Comparing ./master_artifact/chip-shell.elf and ./pull_artifact/chip-shell.elf:

sections,vmsize,filesize

Comparing ./master_artifact/chip-lock.elf and ./pull_artifact/chip-lock.elf:

sections,vmsize,filesize
.debug_info,0,610
.symtab,0,48
.debug_str,0,43
.strtab,0,18
.debug_abbrev,0,8
text,4,4
.shstrtab,0,2
device_handles,-4,-4
.debug_aranges,0,-24
.debug_frame,0,-116
.debug_ranges,0,-296
.debug_line,0,-474
.debug_loc,0,-639

[github-actions]

Size increase report for "esp32-example-build" from 5d2654a

File	Section	File	VM
chip-bridge-app.elf	.flash.text	24	24
chip-temperature-measurement-app.elf	.flash.text	-4	-4
chip-lock-app.elf	.flash.text	24	24
chip-all-clusters-app.elf	.flash.text	12	12
chip-ipv6only-app.elf	.flash.text	172	172

Full report output

BLOAT REPORT

Files found only in the build output:
    report.csv

Comparing ./master_artifact/chip-bridge-app.elf and ./pull_artifact/chip-bridge-app.elf:

sections,vmsize,filesize
[Unmapped],0,4072
.symtab,0,80
.strtab,0,70
.debug_str,0,40
[ELF Section Headers],0,40
.xt.prop._ZN4chip6System21PacketBufferTLVReader4InitEONS0_18PacketBufferHandleE,0,36
.xt.prop._ZN4chip6System21PacketBufferTLVReaderC2Ev,0,36
.flash.text,24,24
.xt.prop._ZN4chip6System27TLVPacketBufferBackingStoreD5Ev,0,12
.xt.lit._ZN4chip6System27TLVPacketBufferBackingStoreD5Ev,0,8
.debug_abbrev,0,-12
.shstrtab,0,-22
.debug_aranges,0,-24
.xt.prop._ZN4chip6System21PacketBufferTLVReader4InitEONS0_18PacketBufferHandleEb,0,-36
.debug_info,0,-58
.xt.prop._ZN4chip6System27TLVPacketBufferBackingStore4InitEONS0_18PacketBufferHandleEb,0,-60
.debug_frame,0,-72
.debug_ranges,0,-464
.debug_loc,0,-742
.debug_line,0,-1052

Comparing ./master_artifact/chip-temperature-measurement-app.elf and ./pull_artifact/chip-temperature-measurement-app.elf:

sections,vmsize,filesize
.strtab,0,80
.symtab,0,80
.debug_str,0,40
[ELF Section Headers],0,40
.xt.prop._ZN4chip6System21PacketBufferTLVReader4InitEONS0_18PacketBufferHandleE,0,36
.xt.prop._ZN4chip6System21PacketBufferTLVReaderC2Ev,0,36
.xt.prop._ZN4chip6System27TLVPacketBufferBackingStoreD5Ev,0,12
.xt.lit._ZN4chip6System27TLVPacketBufferBackingStoreD5Ev,0,8
[Unmapped],0,4
.flash.text,-4,-4
.debug_abbrev,0,-12
.shstrtab,0,-20
.debug_aranges,0,-24
.xt.prop._ZN4chip6System21PacketBufferTLVReader4InitEONS0_18PacketBufferHandleEb,0,-36
.debug_info,0,-57
.xt.prop._ZN4chip6System27TLVPacketBufferBackingStore4InitEONS0_18PacketBufferHandleEb,0,-60
.debug_frame,0,-72
.debug_ranges,0,-464
.debug_loc,0,-743
.debug_line,0,-1080

Comparing ./master_artifact/chip-lock-app.elf and ./pull_artifact/chip-lock-app.elf:

sections,vmsize,filesize
.symtab,0,80
.strtab,0,70
.debug_str,0,44
[ELF Section Headers],0,40
.xt.prop._ZN4chip6System21PacketBufferTLVReader4InitEONS0_18PacketBufferHandleE,0,36
.xt.prop._ZN4chip6System21PacketBufferTLVReaderC2Ev,0,36
.flash.text,24,24
.xt.prop._ZN4chip6System27TLVPacketBufferBackingStoreD5Ev,0,12
.xt.lit._ZN4chip6System27TLVPacketBufferBackingStoreD5Ev,0,8
.debug_abbrev,0,-12
.shstrtab,0,-22
.debug_aranges,0,-24
[Unmapped],0,-24
.xt.prop._ZN4chip6System21PacketBufferTLVReader4InitEONS0_18PacketBufferHandleEb,0,-36
.xt.prop._ZN4chip6System27TLVPacketBufferBackingStore4InitEONS0_18PacketBufferHandleEb,0,-60
.debug_info,0,-69
.debug_frame,0,-72
.debug_ranges,0,-464
.debug_loc,0,-883
.debug_line,0,-1052

Comparing ./master_artifact/chip-pigweed-app.elf and ./pull_artifact/chip-pigweed-app.elf:

sections,vmsize,filesize

Comparing ./master_artifact/chip-all-clusters-app.elf and ./pull_artifact/chip-all-clusters-app.elf:

sections,vmsize,filesize
.debug_info,0,409
.strtab,0,71
.symtab,0,64
.debug_str,0,43
.flash.text,12,12
.shstrtab,0,1
.debug_abbrev,0,-12
[Unmapped],0,-12
.debug_aranges,0,-24
.debug_frame,0,-120
.debug_ranges,0,-160
.debug_line,0,-583
.debug_loc,0,-989

Comparing ./master_artifact/chip-persistent-storage.elf and ./pull_artifact/chip-persistent-storage.elf:

sections,vmsize,filesize

Comparing ./master_artifact/chip-shell.elf and ./pull_artifact/chip-shell.elf:

sections,vmsize,filesize

Comparing ./master_artifact/chip-ipv6only-app.elf and ./pull_artifact/chip-ipv6only-app.elf:

sections,vmsize,filesize
[Unmapped],0,3924
.flash.text,172,172

[bzbarsky-apple]

@msandstedt @saurabhst @LuDuda @jmartinez-silabs Please take a look?