Use a separate color for the current match while searching

[adrsm108]

Is your feature request related to a problem? Please describe.
In vim, incremental search uses the separate IncSearch highlight group to distinguish the current match from other matches. VSCode's native find command has a similar feature, using editor.findMatchBackground for the current match and editor.findMatchHighlightBackground for other matches. Currently, //? in VSCodeVim use the same color for every match in view, which can make it difficult to tell where the cursor will move if the search is confirmed.

Describe the solution you'd like
I'd like the / and ? commands to use a separate decoration for the current match when incsearch is enabled. It would be nice if this defaulted to editor.findMatchBackground, but came with the option to specify background and foreground colors like with vim.searchHighlightColor and vim.searchHighlightTextColor.

Describe alternatives you've considered
Using the native find command gives a similar effect, but always moves the cursor, and isn't integrated with the rest of the extension.

Additional context
Related to #4837, which would support changing the current match before confirming the search. Also somewhat related to #4934, as vim uses the same highlight group for text to be replaced with :s///c.