[lib] Change type of ThinRawThreadInfo.members from MemberInfoWithPermissions to MemberInfoSansPermissions

Summary:
Start of stack replacing stack that started with D12469.

This diff makes the change to ThinRawThreadInfo.members which intentionally introduces flow issues which will be addressed in the rest of the stack.

Also snuck in stripping out MemberInfo.permissions from test data to reduce flow noise.

We're at 5 flow issues instead of the ~64 we had after D12469. Think this is largely due to stack ending in D12496, but will check each of the places with flow issues in previous stack to make sure nothing is broken quietly.

Depends on D12554

Test Plan:
NA, flow.

This change ONLY changes flow types. We still need to update validators, persisted data, keyserver endpoint, client migrations, etc. which will be handled in subsequent diffs.

Reviewers: ashoat

Reviewed By: ashoat

Subscribers: tomek

Differential Revision: https://phab.comm.dev/D12594