Proposed changes

• Decouple script parsing from the revision grid. This will allow easier and simpler integration of other controls with the script manager (e.g. the left panel or the file tree)
• Extract user script binding to a context menu to an extension method. This will allow re-use of the functionality in other parts of the app (e.g. the left panel or the file tree). This is small step in the same direction as WIP: Add 'Run script' command to branches pane context menu #6348 proposed by @IvanGreK. Sadly we stalled on this work.
• Review the code and add multiple validations and add tests.

This work is foundational to allow re-use of user scripts in other parts of the app (e.g. the left panel or the file tree). Specifically I want to allow users to run custom scripts for files in the working tree, e.g. to achieve what was proposed in #6135, or open a file and/or folder in VS Code, or launch a project in a VS.

✒️ I contribute this code under The Developer Certificate of Origin.