Feat: diff view can manipulate selected range

[susiwen8]

This PR fixes #88369 also fixes #9475

[susiwen8]

Need to update test

[alexdima]

Sorry, absolutely not a good change.

For example, for a file with 1000 lines where all 1000 lines are changed by one character, this PR would allocate 1 million LineChange objects.

Looking at the issue you are trying to fix and the location where you propose code changes, I think there is a misunderstanding. The diffComputer should not be touched. The problem of intersecting a selection with a diff change needs to be solved in the git specific action that stages/unstages hunks. So the git actions need to take a linechange and "trim" it to the selected text. It should not be the diff computer (which is performance sensitive) allocate an object per changed line.

[susiwen8]

Yes, that is a big issue, I'm going to close this PR.