Add manual "analyze" button

[imadjarov-quantinuum]

There are a few existing issues with Pylance that boil down to Pylance failing to be "triggered" to analyze files (i.e. it fails to highlight syntax upon opening files, selecting kernels, etc). I've opened some of these issues, e.g., here:

#6972

microsoft/vscode-jupyter#16112

A general solution to such problems, and a useful feature in general, would be to add a button to the bottom toolbar to manually trigger Pylance to analyze a file. This way a user can force analysis when automatic triggering fails.