IDEA: zstd sourcemaps compression

[szokeasaurusrex]

• Compress sourcemaps with zstd
• The manifest gets compressed with gzip
• Assumption here is that backend supports reading gzip from a zip file, but not zstd. However, symbolicator can read zstd
• If the backend is upgraded to Python 3.14, we would have zstd support

[linear[bot]]

CLI-216