[sync] Raw transact

[grigoryk]

Tolstoy needs to be able to assert datoms derived from a set of (inserted) remote transactions.

[rnewman]

There are two definitions of this:

1. Just like normal transact, but with the txInstant specified (which is an open TODO) and a fixed tx ID (which is a function parameter).
2. Bypassing all of the expensive upsert, tempid, etc. mechanics that most of transact does. We're in the process of adding transact_terms, which is closer, but this would be an even lower layer, transacting TermWithoutTempIds — which touches on [sync] Local transaction read client #508, as TermWithoutTempIds is Term<KnownTempId, TypedValue>, a raw representation of a datom.

[grigoryk]

Completed in #563. Not in the most optimal way, but it works.