Consolidate file filtering logic between rsync and bucket upload

[cg505]

Current situation:

• For storage upload to a bucket, we have custom logic that gets the list of files to exclude based on .skyignore/.gitignore, in storage_utils.py
• For rsync to a node, we use the --filter argument to rsync with the .skyignore/.gitignore, which may not follow the same logic.

  skypilot/sky/utils/command_runner.py

  Lines 26 to 33 in a4d94aa

  	# Legend
  	# dir-merge: ignore file can appear in any subdir, applies to that
  	# subdir downwards
  	# Note that "-" is mandatory for rsync and means all patterns in the ignore
  	# files are treated as *exclude* patterns. Non-exclude patterns, e.g., "!
  	# do_not_exclude" doesn't work, even though git allows it.
  	RSYNC_FILTER_SKYIGNORE = f'--filter=\'dir-merge,- {constants.SKY_IGNORE_FILE}\''
  	RSYNC_FILTER_GITIGNORE = f'--filter=\'dir-merge,- {constants.GIT_IGNORE_FILE}\''

We should use the same logic everywhere. Since we can't use the rsync --filter arg during bucket upload, we should use the custom logic.