fix: add selection to next find match (CTRD + D) not working with Regex Find Mode (#107090)

[BrunoSoaresEngineering]

Solves #107090 .

Solved by passing isRegex flag from findController to MultiCursorSession as much like the wholeWord and matchCase flags.

Added unit test to specifically test this issue. While writing the unit test, I identified another potential issue: while adding selection to next find match using the find controller, the selection range that was there, previous to the change of focus to the find input box, is not released. That is the reason I had to add the [1, 1, 1, 1] range to the expected selections array in the unit test assertion. Since this issue has a different root cause, I am opening a new issue to tackle this separately.

I appreciate a lot your feedback in advance,

[BrunoSoaresEngineering]

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