tab collection storage implementation.

This CL has -

1. the initial implementation of TabCollectionStorage. Some of the collection related methods will be implemented later along with the implementation of specific tab collection classes.

2. A basic pinned tab collection with mostly non implemented methods. This is to help with the unittest for tab collection storage instead of using a fake class/ mock.

Change-Id: Idcdc38b2dc2fa3e3658cdf39b5479c883e7ce4a1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5320080


Reviewed-by: Taylor Bergquist <tbergquist@chromium.org>
Commit-Queue: Shibalik Mohapatra <shibalik@chromium.org>
Reviewed-by: David Pennington <dpenning@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1266852}