UI copy discrepancies on right click and slash command menu in IDE

Problems to solve

There are small inconsistencies in the UI copy on menus in VS Code and the Web IDE. This issue proposes making the UI copy more consistent.

Image	Description
	We should be consistent and say selected code everywhere or nowhere
	We use sentence case (docs style guide, Pajamas capitalization)
	Inconsistencies in generate versus write tests. Inconsistencies in the use of selected code versus selected snippet