Add gB keybinding for finding the previous match

[musjj]

Fix: #9000

What this PR does / why we need it:

gb is a nice binding, so the inverse of it would be useful.

You can bind editor.action.addSelectionToPreviousFindMatch in your config, but the nice thing about the built-in gb is that it aligns all the selection ends of the cursors.

Which issue(s) this PR fixes

fixes #9000

Special notes for your reviewer:

[HenryTSZ]

I merged this PR and tested it locally, and found an issue: When the word are not in current view, It flashed the view to the selected word but jump back to the original one.

prev-find-match.mp4

I discovered the problem through debugging

Vim/src/mode/modeHandler.ts

Lines 1472 to 1475 in 3c33d00

	const isLastCursorTracked =
	this.vimState.recordedState.actionsRun[
	this.vimState.recordedState.actionsRun.length - 1
	] instanceof ActionOverrideCmdD;

You need to add ActionPreviousFindMatch here as well

like this:

      const lastActionRun =
        this.vimState.recordedState.actionsRun[this.vimState.recordedState.actionsRun.length - 1];
      const isLastCursorTracked =
        lastActionRun instanceof ActionOverrideCmdD ||
        lastActionRun instanceof ActionPreviousFindMatch;