Revert "[shell] enable shell as an optional module in apps (#7080)"

[bzbarsky-apple]

This reverts commit c8f286f because
the result does not compile.

Fixes #7200

Problem

Tree does not build.

Change overview

Revert the PR that makes it not build.

Testing

How was this tested? (at least one bullet point required)

• ./gn_build.sh run locally at toplevel of the tree.

[github-actions]

Size increase report for "nrfconnect-example-build" from c2cc13d

File	Section	File	VM
chip-shell.elf	device_handles	8	8
chip-shell.elf	text	8	8

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
.debug_loc,0,533
.debug_str,0,311
.strtab,0,222
.symtab,0,208
.debug_frame,0,132
.debug_aranges,0,48
.debug_ranges,0,24
.debug_line,0,11
device_handles,8,8
text,8,8
.shstrtab,0,2
.debug_abbrev,0,-450
.debug_info,0,-2193

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

sections,vmsize,filesize

[bzbarsky-apple]

Addressed by #7205