Remove redundant BufReaders for decompressing tar archives

[kskalski]

Problem

ZSTD Decoder::new creates buf reader with tuned size already, other decoders handle buffering too:

• BzDecoder https://docs.rs/bzip2/latest/src/bzip2/read.rs.html#87-91
• GzDecoder https://docs.rs/flate2/latest/src/flate2/gz/read.rs.html#143-147
• lz4::Decoder https://docs.rs/lz4/1.28.1/src/lz4/decoder.rs.html#33-43 (it uses a vec buffer directly)
• zstd::Decoder https://github.com/gyscos/zstd-rs/blob/229054099aa73f7e861762f687d7e07cac1d9b3b/src/stream/read/mod.rs#L29

In those cases wrapping reader with BufReader is counter-productive or unnecessary (bzip2 provides both bufread and read decoders)

Summary of Changes

Remove redundant BufReaders for decompressing tar archives when underlying decompressor is already doing buffering.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 25.00000% with 3 lines in your changes missing coverage. Please review.

Project coverage is 82.8%. Comparing base (103fb21) to head (71e2436).
Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff            @@
##           master    #6317     +/-   ##
=========================================
- Coverage    82.8%    82.8%   -0.1%     
=========================================
  Files         847      847             
  Lines      379488   379486      -2     
=========================================
- Hits       314349   314309     -40     
- Misses      65139    65177     +38     

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[brooksprumo]

ZSTD Decoder::new creates buf reader with tuned size already (https://github.com/gyscos/zstd-rs/blob/229054099aa73f7e861762f687d7e07cac1d9b3b/src/stream/read/mod.rs#L29), most others have some form of buffering too, so wrapping reader with BufReader is counter-productive.

Thanks for the link to where zstd creates its own BufReader. Can you also provide links for gzip and lz4 too, since this PR is changing them as well.

[kskalski]

Sure, I'm also switching bzip2 decoder as it has appropriate wrapper. Updated description.

[brooksprumo]

Looks good to me. I think you'll need to rebase to pull in newer commits that fix the CI.

[brooksprumo]

[brooksprumo]

Let's also backport this to v2.3. We'll need to wait for #6430 to land, and then please add the "v2.3" label to kickoff the backport.

[mergify]

Backports to the beta branch are to be avoided unless absolutely necessary for fixing bugs, security issues, and perf regressions. Changes intended for backport should be structured such that a minimum effective diff can be committed separately from any refactoring, plumbing, cleanup, etc that are not strictly necessary to achieve the goal. Any of the latter should go only into master and ride the normal stabilization schedule. Exceptions include CI/metrics changes, CLI improvements and documentation updates on a case by case basis.