[RemoveLegacy] Remove unused `BreakSpaceType`s

This patch changes two `BreakSpaceType` that are no longer
used:
* `kBeforeEverySpace` is the mode for the legacy line breaker.
* `kBeforeSpaceRun` is the mode used by `NGLineBreaker`
  initially, but is no longer used when its `pre-wrap` support
  was improved.

Also, this patch includes:
* Change the default of `LazyLineBreakIterator` to
  `kAfterSpaceRun`.
* Add a constructor that copies settings from another
  `LazyLineBreakIterator`.
* Remove a constructor without arguments, that is only used by
  tests.
* Update unit tests to use `kAfterSpaceRun`.

This patch should have no behavior changes.

Bug: 1229581
Change-Id: I04c420b986c00c4467dc14496f764edf63216b3f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4592378
Reviewed-by: Kent Tamura <tkent@chromium.org>
Commit-Queue: Kent Tamura <tkent@chromium.org>
Auto-Submit: Koji Ishii <kojii@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1154122}