[lib] Add memberInfoSansPermissionsValidator to convertClientDBThreadInfoToRawThreadInfo

Summary:
Added memberInfoSansPermissionsValidator to convertClientDBThreadInfoToRawThreadInfo.

In preparation for client migrations. Moved the more "relevant" validators earlier in conditional so we're doing (almost always) useless legacyMemberInfoValidator check all the time.

Depends on D12779

Test Plan: Will be tested implicitly by client migrations. We have unit tests for memberInfoSansPermissionsValidator.

Reviewers: ashoat, tomek

Reviewed By: ashoat

Differential Revision: https://phab.comm.dev/D12787