Views: ephemeral tables

[Shubham8287]

Description of Changes

Make View backing tables and related St tables not persistent.

1. Modifies CommittedState to hold set of ephemeral tables.
2. Update TxData to contain a subset of ephemeral tables which has been modified in current transaction.

do_durability filter those table out before writting the transaction to commitlog.

depends on: https://github.com/clockworklabs/SpacetimeDB/pull/3651

API and ABI breaking changes

NA

Expected complexity level and risk

2.5.

looks simple but changes comes in the hotpath, I ensured we don't do unneccessary heap allocations but patch has the potential to regress perfomance.

Testing

• unit test.