[iOS] Enable Send Tab notifications when other notifications are enabled

Currently, users are always enrolled in provisional Send Tab
notifications. This CL:
* updates the logic to avoid doing this if users have previously
disabled Send Tab at least once.
* updates to logic to also enable Send Tab if regular
(non-provisional) notification permissions are enabled.

Low-Coverage-Reason: TESTS_IN_SEPARATE_CL
Bug: 343495218
Change-Id: Ia07bdbc902fa6db0fb138827ddaf1407359955d1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5857027
Reviewed-by: Guillem Perez <guiperez@google.com>
Commit-Queue: Hira Mahmood <hiramahmood@google.com>
Reviewed-by: Guillaume Jenkins <gujen@google.com>
Cr-Commit-Position: refs/heads/main@{#1355297}