deflate: Better Huffman.construct errors and error handling

[squeek502]

This brings Huffman.construct error handling in line with puff.c (I'm assuming we're okay with treating puff.c as an oracle). The error names and logic are from puff.c (and zlib's inflate.c uses the same terminology).

Note: I am planning to add relevant test cases soon. EDIT: Done

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This is the last piece of the puzzle for getting the deflate.zig <-> puff.c comparison fuzzer (which checks that all inputs either give the same inflated output or give errors in both implementations) to run cleanly (so far at least). Other required puzzle pieces:

• deflate.zig: check for distances past beginning of output stream #9860 (not yet merged)
• deflate.zig: fix bits_left overflow at EndOfStream and @intCast truncation with empty Huffman table #9849

cc @LemonBoy @mattbork

[squeek502]

Test cases added. Note that #9860 should almost certainly be merged before this (I tested locally with those changes included, so if this PR fails in CI then it's likely because #9860 needs to be merged first).

[LemonBoy]

Minor nit, why not move the check below the loop that computes left?

[squeek502]

I didn't want to potentially leave self.last_code/self.last_index uninitialized since error.IncompleteSet is not always treated as an error by the caller, and if decode uses those fields when uninitialized it can lead to index-out-of-bounds/UB.