Tree: Support moving the find widget vertically

[memeplex]

Does this issue occur when all extensions are disabled?: Yes

• VS Code Version: 1.70.2
• OS Version: macOS Monterey

Steps to Reproduce:

1. In the file explorer press cmd-f
2. Write something such that only one match remains in the tree
3. Now the filter partially hides the match and there's no way to get rid of it without destroying the filter:

[gjsjohnmurray]

Maybe we should allow one row of vertical movement for the floating find widget.

@joaomoreno what do you think? If you agree I can provide a PR.

[joaomoreno]

Sure why not!