dolt system tables do not consider remote refs

Dolt system tables typically ignore remote refs, and this is problematic when attempting to implement some basic functionality that is aware of remotes.
For example, the [`dolt_branches` table](https://docs.dolthub.com/sql-reference/version-control/dolt-system-tables#dolt_branches) does not indicate that a particular branch is tracking a remote branch. This information is currently only available in the `repo_state.json` repo file.
Similarly, the [`dolt_commits` table](https://docs.dolthub.com/sql-reference/version-control/dolt-system-tables#dolt_commits) only deals with local commits, and it is currently not possible to get a list of remote commits.