improve addon-dev clean

[patricklx]

this now only updates changed files in dist. And deletes removed files in dist. otherwise all files are deleted on each change, which makes HMR less useful

[patricklx]

so one thing that I would like to do before we actually move forward on this is that we verify that this Plugin works correctly with the bug scenario that #1448 was originally trying to fix. Ideally we would cover this in the v2 addon dev watch tests

I think what this actually does now is more like a sync. When a file gets deleted in src, the corresponding generated file in dist also gets deleted. there is the option runOnce https://github.com/vladshcherbin/rollup-plugin-delete?tab=readme-ov-file#runonce, which only deletes the files only once at start. Which is already better, but it leaves the deleted files during dev.

I think this also fixes the original issue. As long as files are copied as part of the bundle, by e.g emit, and not using manual copy. This will work correctly.

[mansona]

I think this also fixes the original issue

The problem I have with this PR is that I want more confidence that it fixes the original issue before we move forward with it. Myself and @NullVoxPopuli tried to recreate the issue on the Triage meeting and we couldn't get it to fail so we can't tell if this makes any difference 🙃

I would really like a failing test that shows the problem in a repeatable way before we try to fix it by altering the underlying implementation. If this is not possible (because maybe it's an OS level race condition 🤷) then at the very least we need to coordinate with @simonihmig because he said he would be looking into the original issue over the next while: https://github.com/embroider-build/addon-blueprint/issues/32#issuecomment-2079582665

[patricklx]

I'm not sure how to add a test for this

[patricklx]

@mansona i improved this even more and added some tests