Allow to exclude files from worktrees

[SomeoneToIgnore]

• Part of Project-specific settings for including / excluding directories and files #5443

Allows to fully remove from Zed certain files or file groups: no items will be scanned or added into worktrees, so nothing will be shown in project tree, project search and go to file would not see those, corresponding FS events will be ignored.

One exclusion is .git files: those are still not shown or accessible by default, yet tracked in the worktrees.

By default, is configured to

  "file_scan_exclusions": [
    "**/.git",
    "**/.svn",
    "**/.hg",
    "**/CVS",
    "**/.DS_Store",
    "**/Thumbs.db",
    "**/.classpath",
    "**/.settings"
  ],

• In addition, contains code preparations for "search in included files" feature: new SearchOptions variant, search crate and RPC adjustments

Release Notes:

• Added file_scan_exclusions section to project settings to completely ignore certain files in Zed