Diff View: Scroll to center of hunks when reviewing (#25846)

When reviewing hunks, scroll to put them at the center of the screen
so you can better see the context around that hunk.

The field `center_cursor` was added to the actions `editor::GoToHunk`
and `editor::GoToPrevHunk`, this was set to `false` by default in
keymaps, as it wouldn't help with in-editor navigation.

The field is set to `true` for when you trigger `git::StageAndNext`
and `git::UnstageAndNext`, this is also `true` for the buttons in the
Diff View toolbar.

Release Notes:

- N/A

assets/keymaps/macos/jetbrains.json

@@ -40,8 +40,8 @@
       "cmd-alt-shift-b": "editor::GoToTypeDefinitionSplit",
       "f2": "editor::GoToDiagnostic",
       "shift-f2": "editor::GoToPrevDiagnostic",
-      "ctrl-alt-shift-down": "editor::GoToHunk",
-      "ctrl-alt-shift-up": "editor::GoToPrevHunk",
+      "ctrl-alt-shift-down": ["editor::GoToHunk", { "center_cursor": true }],
+      "ctrl-alt-shift-up": ["editor::GoToPrevHunk", { "center_cursor": true }],
       "cmd-home": "editor::MoveToBeginning",
       "cmd-end": "editor::MoveToEnd",
       "cmd-shift-home": "editor::SelectToBeginning",

assets/keymaps/macos/sublime_text.json

@@ -44,8 +44,8 @@
       "alt-cmd-down": "editor::GoToDefinition",
       "ctrl-alt-cmd-down": "editor::GoToDefinitionSplit",
       "alt-shift-cmd-down": "editor::FindAllReferences",
-      "ctrl-.": "editor::GoToHunk",
-      "ctrl-,": "editor::GoToPrevHunk",
+      "ctrl-.": ["editor::GoToHunk", { "center_cursor": true }],
+      "ctrl-,": ["editor::GoToPrevHunk", { "center_cursor": true }],
       "cmd-k cmd-u": "editor::ConvertToUpperCase",
       "cmd-k cmd-l": "editor::ConvertToLowerCase",
       "cmd-shift-j": "editor::JoinLines",