[native] Update updateRolesAndPermissions to only handle LegacyRawThreadInfos

Summary:
Similar to what we did in D10283, we're "lying" to flow and saying that updatedRolesAndPermissions (which we also rename legacyUpdateRolesAndPermissions) accepts RawThreadInfos instead of just LegacyRawThreadInfos. However, we call assertAllThreadInfosAreLegacy right at the start of legacyUpdateRolesAndPermissions to ensure that only LegacyRawThreadInfos are passed to this function.

It could be argued that this is worse than D10283, because it's unlikely that we'd want to run the convertThreadStoreThreadInfosToNewIDSchema migration again, whereas it's VERY likely that we'll want to run updateRolesAndPermissions in the future. I will introduce a new version of updateRolesAndPermissions that'll handle MinimallyEncodedRawThreadInfos (by going through and converting all to LegacyRawThreadInfos which is what the logic in this migration requires since that's what eg getRolePermissionBlobs and makePermissionsBlob deal with. I'll put that up as a followup diff in this stack (probably before landing anything).

However, as of this diff we're now at 0 flow issues in native/web/keyserver/lib.

Depends on D10283

Test Plan: CI, flow, etc. I think in the future it would be nice to have unit tests for migrations.

Reviewers: ashoat, ginsu, tomek, rohan

Reviewed By: ashoat

Differential Revision: https://phab.comm.dev/D10284