ci(rust): check MSRV in CI and fix clippy

[wjones127]

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[wjones127]

I'm struggling to understand what's going on with clippy. I get errors when I run it locally, even with the same version of clippy:

❯ cargo clippy --version
clippy 0.1.81 (eeb90cda 2024-09-04)
❯ cargo clippy --features cli,dynamodb,tensorflow,dynamodb_tests --tests --benches -- -D warnings
    Checking lance-arrow v0.19.2 (/Users/willjones/Documents/lance/rust/lance-arrow)
   Compiling lance-encoding v0.19.2 (/Users/willjones/Documents/lance/rust/lance-encoding)
   ...
    Checking lance-io v0.19.2 (/Users/willjones/Documents/lance/rust/lance-io)
    Checking lance-datafusion v0.19.2 (/Users/willjones/Documents/lance/rust/lance-datafusion)
error: this could be rewritten as `let...else`
   --> rust/lance-index/src/scalar/inverted/builder.rs:455:13
    |
455 | /             let token = if let Some(token) = token {
456 | |                 token
457 | |             } else {
458 | |                 continue;
459 | |             };
    | |______________^
    |
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#manual_let_else
    = note: `-D clippy::manual-let-else` implied by `-D warnings`
    = help: to override `-D warnings` add `#[allow(clippy::manual_let_else)]`
help: consider writing
    |
455 ~             let Some(token) = token else {
456 +                 continue;
457 +             };
    |

error: pub(crate) struct inside private module
   --> rust/lance-index/src/scalar/inverted/builder.rs:564:1
    |
564 | pub(crate) struct PostingReader {
    | ----------^^^^^^^^^^^^^^^^^^^^^
    | |
    | help: consider using: `pub`
    |
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#redundant_pub_crate
    = note: `-D clippy::redundant-pub-crate` implied by `-D warnings`
    = help: to override `-D warnings` add `#[allow(clippy::redundant_pub_crate)]`

error: pub(crate) function inside private module
   --> rust/lance-index/src/scalar/inverted/builder.rs:708:1
    |
708 | pub(crate) fn inverted_list_schema(with_position: bool) -> SchemaRef {
    | ----------^^^^^^^^^^^^^^^^^^^^^^^^
    | |
    | help: consider using: `pub`
    |
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#redundant_pub_crate

error: unnecessary structure name repetition
  --> rust/lance-index/src/scalar/inverted/tokenizer.rs:49:9
   |
49 |         TokenizerConfig {
   |         ^^^^^^^^^^^^^^^ help: use the applicable keyword: `Self`
   |
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#use_self
   = note: `-D clippy::use-self` implied by `-D warnings`
   = help: to override `-D warnings` add `#[allow(clippy::use_self)]`

error: could not compile `lance-index` (lib) due to 4 previous errors
warning: build failed, waiting for other jobs to finish...
error: could not compile `lance-index` (lib test) due to 4 previous errors

[wjones127]

For whatever reason, these flags weren't being picked up in CI. So I've moved them to Cargo.toml, which seems to work.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 86.79245% with 14 lines in your changes missing coverage. Please review.

Project coverage is 77.54%. Comparing base (66c5f2c) to head (7464e19).

Files with missing lines	Patch %	Lines
rust/lance/src/dataset/transaction.rs	72.72%	3 Missing ⚠️
rust/lance-datafusion/src/exec.rs	33.33%	2 Missing ⚠️
rust/lance-arrow/src/deepcopy.rs	0.00%	1 Missing ⚠️
rust/lance-datafusion/src/planner.rs	80.00%	0 Missing and 1 partial ⚠️
rust/lance-encoding-datafusion/src/lib.rs	0.00%	1 Missing ⚠️
rust/lance-encoding/src/decoder.rs	75.00%	1 Missing ⚠️
rust/lance-io/src/object_store.rs	0.00%	0 Missing and 1 partial ⚠️
rust/lance/src/dataset/write/merge_insert.rs	50.00%	1 Missing ⚠️
rust/lance/src/dataset/write/update.rs	66.66%	0 Missing and 1 partial ⚠️
rust/lance/src/index/vector/pq.rs	66.66%	1 Missing ⚠️
... and 1 more

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3054      +/-   ##
==========================================
- Coverage   77.61%   77.54%   -0.08%     
==========================================
  Files         240      240              
  Lines       78683    78573     -110     
  Branches    78683    78573     -110     
==========================================
- Hits        61073    60931     -142     
- Misses      14495    14504       +9     
- Partials     3115     3138      +23     

Flag	Coverage Δ
unittests	77.54% <86.79%> (-0.08%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

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[westonpace]

Thanks for digging in and figuring this out. It was annoying me as well :)