Reformat components/sync/

The ModelType->DataType rename caused some formatting havoc because
`git cl format` doesn't format renamed files, even if they had changes.
This CL reformats all *.h and *.cc files in components/sync. This also
uncovers some issues which are then fixed manually, namely:
- Anonymous namespaces that had nothing in them, and so are deleted.
- A test file with no tests (data_type_state_helper_unittest.cc), which
  is deleted.

Most of the diff is due to braces becoming mandatory for ifs and loops.

Low-Coverage-Reason: TRIVIAL_CHANGE Just reformatting.
Bug: 356649891
Change-Id: I5bc16728b8416f2f7f3998ac6ac33b6e51621cc5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5854403
Commit-Queue: Rushan Suleymanov <rushans@google.com>
Auto-Submit: Victor Vianna <victorvianna@google.com>
Reviewed-by: Rushan Suleymanov <rushans@google.com>
Cr-Commit-Position: refs/heads/main@{#1354405}