Move dirty from Context to EagerDir

[mbouaziz]

For typed directories, ideally we'd need to keep keys and files in directories to avoid unsafe casts. There are a few cases of keys in the Context, some are more or less problematic.

This move looks safe as dirty is only accessed in update, and only updated in writeEntry with no weird interleaving with setDir.

Ideally, I'd do the same with dirtyReaders but there are too many interleavings, so there's a risk to exist a setDir between a change and another setDir, then missing some changes.

[mbouaziz]

The failure on skdb-wasm looks non-transient, I can replicate it locally though I have no idea how this diff produces a RuntimeError: memory access out of bounds

[skiplabsdaniel]

The failure on skdb-wasm looks non-transient, I can replicate it locally though I have no idea how this diff produces a RuntimeError: memory access out of bounds
If it's 'Write-csv memory regression test' it's probably because the diff consume more memory.

[mbouaziz]

Thanks for the heads-up!
It looks like this diff has a big bad impact on memory consumption, probably because its peak temporary garbage is higher.