Log exception type when mail sync dies.
Directly filter messages by namespace_id for API queries.

Summary:
Now that messages have a namespace_id, we don't need to do the wonky
joining-to-threads thing. This makes the /messages endpoint two to three times
faster on large mailboxes.

Test Plan: Unit tests.

Reviewers: khamidou

Reviewed By: khamidou

Differential Revision: https://review.inboxapp.com/D539
[sentry] Whitelist stack locals

Summary: Stack locals contain valuable debugging information. Keep some of them which are not PII (so far, only `account_id`).

Test Plan: Triggered an exception, tested that locals got stripped.

Reviewers: dlitz, emfree

Reviewed By: emfree

Projects: #sync-engine

Differential Revision: https://review.inboxapp.com/D546
Validate recipients before sending a draft.

Summary:
We shouldn't let people try to send drafts when the recipients are patently
invalid. So check them before sending.

Test Plan: Unit test added.

Reviewers: khamidou

Reviewed By: khamidou

Differential Revision: https://review.inboxapp.com/D544
Migration for new easaccount.eas_state
Fix typo
Drop eas_state column