Add `ProcedureContext::with_tx`

[Centril]

Description of Changes

Adds ProcedureContext::{with_tx, try_with_tx}.

Fixes https://github.com/clockworklabs/SpacetimeDB/issues/3515.

API and ABI breaking changes

None

Expected complexity level and risk

2

Testing

An integration test test_calling_with_tx is added.