v2.3: Remove redundant BufReaders for decompressing tar archives (backport of #6317)

[mergify]

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.

---

This is an automatic backport of pull request #6317 done by [Mergify](https://mergify.com).

[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 (de54ce0) to head (8d1fdd8).
Report is 1 commits behind head on v2.3.

Additional details and impacted files

@@            Coverage Diff            @@
##             v2.3    #6453     +/-   ##
=========================================
- Coverage    82.8%    82.8%   -0.1%     
=========================================
  Files         848      848             
  Lines      379479   379477      -2     
=========================================
- Hits       314550   314503     -47     
- Misses      64929    64974     +45     

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[brooksprumo]

@Mergifyio rebase

[mergify]

rebase

✅ Branch has been successfully rebased