[lib] Introduce persistedRoleInfoValidator and use in convertClientDBThreadInfoToRawThreadInfo

Summary:
In convertClientDBThreadInfoToRawThreadInfo we validate contents of persisted RoleInfos before any migrations are run. After removing isDefault from RoleInfo and roleInfoValidator, we need to handle case where user has persisted RoleInfos WITH the isDefault field included. Otherwise we'll get an error something like this:

Depends on D11276

Test Plan:

• Unit test
• Installed and logged into old version of native
• Updated to master, observed that I didn't see the message above:

Reviewers: ginsu, tomek, michal, kamil

Reviewed By: tomek

Subscribers: ashoat

Differential Revision: https://phab.comm.dev/D11286