cli: add a test of `hg debugnodemap --manifest` this is a new option that's not tested yet

cli: fix spelling in `debugnodemap` error messages

cli: make debugnodemap capable of inspecting an arbitrary nodemap This lets us inspect the manifest nodemap and individual directory nodemaps when treemanifest is used.

rust: mostly avoid streaming zstd decompression Streaming ZStd decompression seems slightly slower, and the API we use makes it very inconvenient to re-use the decompression context. Instead of using that, use the buffer-backed version, because we can give a reasonable-ish size estimate.

rust: in zstd decompression, avoid a useless vec initialization

rust: speed up zstd decompression by re-using the decompression context Admittedly, zstd is already pretty fast, but this change makes it a bit faster yet: it saves ~5% of time it takes to read our large repo. The actual motivating use case is treemanifest: in treemanifest we end up reading *lots* of small directories, and many of them need decompression, and there the saving for [rhg files] is >10%. (which also seems unreasonable, we should probably keep things uncompressed more)