Add a .tar.gz bundle loader

[sandhose]

This adds an (optional) .tar.gz bundle loader, exposed in the library behind the loader feature. It's a fully async one, and only loads what's needed from the tar.

It also adds that capability to the CLI, by adding a --bundle flag. I also went ahead and changed the PathBufs in the CLI to camino's Utf8PathBuf, because it's a mess to have to deal with OsStrings, and not worth it.

@jondot: You might want to take a look to use that in the integration tests

[codecov-commenter]

Codecov Report

Merging #8 (119f100) into main (e48e51e) will decrease coverage by 0.05%.
The diff coverage is 0.00%.

@@           Coverage Diff            @@
##            main      #8      +/-   ##
========================================
- Coverage   2.42%   2.36%   -0.06%     
========================================
  Files         30      31       +1     
  Lines       1443    1478      +35     
========================================
  Hits          35      35              
- Misses      1408    1443      +35     

Impacted Files	Coverage Δ
src/bin/opa-eval.rs	1.51% <0.00%> (-0.10%)	⬇️
src/bin/simple.rs	5.26% <ø> (ø)
src/builtins/impls/base64url.rs	0.00% <ø> (ø)
src/builtins/impls/crypto.rs	0.00% <ø> (ø)
src/builtins/impls/glob.rs	0.00% <ø> (ø)
src/builtins/impls/graph.rs	0.00% <ø> (ø)
src/builtins/impls/graphql.rs	0.00% <ø> (ø)
src/builtins/impls/hex.rs	0.00% <ø> (ø)
src/builtins/impls/http.rs	0.00% <ø> (ø)
src/builtins/impls/io.rs	0.00% <ø> (ø)
... and 21 more

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