Compress release bundle with zstandard/zstd to reduce size

[DSmithVA]

I propose a .zstd download option alongside the existing .gz one for Linux releases. For the latest 2.18.1 linux64 bundle, using zstd instead of gzip can cut off 33% of the file size, or 822.8 MiB down to 553.2 MiB.

Example command to convert the existing .gz:
zcat codeql-bundle-linux64.tar.gz | zstd --long=27 -9 -o codeql-bundle-linux64.tar.zstd

File sizes:
862823301 codeql-bundle-linux64.tar.gz
580124258 codeql-bundle-linux64.tar.zstd

For zstd arguments, compression levels above -9 saw diminishing returns, though -19 does get down to 504.5 MiB while taking 12x longer to compress. Using higher --long= values improves compression, but 27 is the highest value that clients can process by default, per https://github.com/facebook/zstd/blob/dev/programs/zstd.1.md?plain=1#L162

Compression with xz is also an improvement, it's just noticeably slower. Either is an improvement over just .gz and any recent linux will support both .zstd or .xz for decompression.

[jketema]

Thanks for your feedback. We'll take this into consideration.