Add (currently hidden, off by default) config option for emulating the Vim command bar in Kate vim mode, and set it at the beginning of the new VimStyleCommandBarTests. Introduce KateViEmulatedCommandBar class, and add it to KateView, along with an accessor. Summon the bar on "/", and ensure that it has correct indicator label and an empty text bar. Test that the typed text appears in the emulatedCommandBarTextEdit when it is summoned.

Use RIAA to set up pre-conditions for the VimStyleCommandBarTests and ensure they are reverted when the test ends.

REVIEW:109867
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