refactor!: Use different Id types

[aawsome]

Breaking change:
Use different Id types for all places where Ids play a role. This makes the source code much more understandable.

This also prevents some nasty kind of bugs. This was possible before:

let snap = repo.get_snapshot_from_str("latest", |_| true)?;
let node = repo.node_from_path(snap.id, "/my/path".into())?;

But this wasn't working as snap.id is a snapshot id and node_from_path requires a tree id. This code will now fail at compile time.

[codecov]

Codecov Report

Attention: Patch coverage is 48.83721% with 66 lines in your changes missing coverage. Please review.

Project coverage is 48.4%. Comparing base (59bd3e5) to head (eb15129).

Files with missing lines	Patch %	Lines
crates/core/src/repository.rs	31.5%	13 Missing ⚠️
crates/core/src/id.rs	35.2%	11 Missing ⚠️
crates/core/src/commands/prune.rs	50.0%	6 Missing ⚠️
crates/core/src/index.rs	40.0%	6 Missing ⚠️
crates/core/src/repofile/packfile.rs	16.6%	5 Missing ⚠️
crates/core/src/blob/packer.rs	57.1%	3 Missing ⚠️
crates/core/src/commands/copy.rs	0.0%	3 Missing ⚠️
crates/core/src/commands/merge.rs	0.0%	3 Missing ⚠️
crates/core/src/repofile/snapshotfile.rs	40.0%	3 Missing ⚠️
crates/core/src/blob.rs	33.3%	2 Missing ⚠️
... and 7 more

Additional details and impacted files

Files with missing lines	Coverage Δ
crates/backend/src/opendal.rs	93.5% <ø> (ø)
crates/core/src/archiver.rs	66.1% <100.0%> (ø)
crates/core/src/archiver/file_archiver.rs	79.1% <100.0%> (ø)
crates/core/src/archiver/parent.rs	66.6% <100.0%> (ø)
crates/core/src/archiver/tree_archiver.rs	73.2% <100.0%> (ø)
crates/core/src/backend.rs	56.1% <100.0%> (-1.4%)	⬇️
crates/core/src/backend/cache.rs	72.7% <100.0%> (-0.7%)	⬇️
crates/core/src/backend/decrypt.rs	67.6% <100.0%> (+0.9%)	⬆️
crates/core/src/backend/node.rs	68.9% <ø> (+5.1%)	⬆️
crates/core/src/blob/tree.rs	66.5% <100.0%> (-1.1%)	⬇️
... and 29 more

... and 6 files with indirect coverage changes

[aawsome]

@simonsan I think this is ready for a review. I did not finish changing all internals where PackedId can be used, but the interface should now just use the Id newtypes.

[simonsan]

Great job! That looks so much cleaner now! A few nits: