Slow search in large files when either hlsearch or incsearch is enabled

[igor-akhmetov]

With both hlsearch noincsearch and nohlsearch incsearch VSCodeVim highlights matches in the entire file after starting a search with /. In large files, this leads to a hang after the first letter is typed since there are many matches. The built-in VS Code text search seems to stop after a predefined number of matches and does not highlight further. With nohlsearch noincsearch there are no highlights and no hang.