zlib: add raw content read methods to ZipEntry

[pipobscure]

zipEntry.rawContent was a getter that exposed the retained buffer of an in-memory entry and returned null for a file-backed or streaming one, so the still-compressed bytes of a member read through ZipFile could not be obtained at all.

Replace it with rawContent(), rawContentSync() and rawContentIterator(), which mirror content(), contentSync() and contentIterator() but return the bytes as stored, without decompressing or verifying them. They work for every entry that has readable content, return caller-owned buffers from the buffered variants, and accept a maxSize bound on the compressed size.

The motivation for this change is that I found a great use-case for this: web serving directly from an archive. If Accept-Encoding: gzip or Accept-Encoding: deflate is presented and the archive already has the part compressed that way, then it can serve that staright without any overhead.

So I decided to make change rawContent from a getter to a function and have the rawContent family of functions match what the content functions do. But since that changesbthe experimental API, it's probably a semver-minor.

@mcollina can you advise if changing the API from getter to function is ok in an experimental thing?

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.49%. Comparing base (f513ec7) to head (8f4a4f9).

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #66801   +/-   ##
=======================================
  Coverage   90.49%   90.49%           
=======================================
  Files         797      797           
  Lines      277686   277738   +52     
  Branches    53362    53370    +8     
=======================================
+ Hits       251292   251348   +56     
+ Misses      16796    16790    -6     
- Partials     9598     9600    +2     

Files with missing lines	Coverage Δ
lib/internal/zip/entry.js	98.60% <100.00%> (+0.46%)	⬆️

... and 32 files with indirect coverage changes

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