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