New Editor with All Found lines improvement: highlight all found occurrences

[MKadaner]

This is follow-up on #955. Copying here relevant discussion from the PR

By @johnd0e in https://github.com/FarGroup/FarManager/issues/955#issuecomment-3025387385

[I]deas for improvement:

2. Highlight found occurrences

By @MKadaner in https://github.com/FarGroup/FarManager/issues/955#issuecomment-3025454574

[D]o you mean to highlight all found patterns? Is it possible? Yes, of course, it should be. Again, please let me know.

By @johnd0e in https://github.com/FarGroup/FarManager/issues/955#issuecomment-3025619532

Yes, I meant exactly that. It can be achieved with ECTL_ADDCOLOR.

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P.S. @alabuzhev, could you please assign this issue to me?

[MKadaner]

Before I start implementing, does anybody want this feature? What is the consensus?