Identifiers: Refactor + Improve type-safety & performance

[Centril]

Description of Changes

The goal of this PR is to:

• Make it easy to switch our backing implementation of identifiers, as seen in the commit changing to LeanString.
• Improve type safety of our identifiers by having every identifier start with RawIdentifier and then Identifier is just a wrapper with validation on construction. TableName and ReducerName are then just wrappers around Identifier.
• Reduce allocation in InstanceEnv by using the now clone-on-write O(1) + SSO optimized Identifier.
• Reduce allocations in the query engine as a consequence of improving RawIdentifier and Identifier.
• Have &'static str strings be further optimized by avoiding to allocate even for long ones. This is supported by impl From<&'static str> for RawIdentifier as well as switching to LeanString.

The PR results in a roughly 2k TPS improvement over master for WASM + hash indices. This should also help V8, as this is VM-agnostic.

API and ABI breaking changes

None

Expected complexity level and risk

3? Mostly just small changes in many places, but in a sea of small changes, mistakes can happen.

Testing

Covered by existing tests.

[Centril]

Next step after this PR and once websocket 2.0 has been merged is to also use the identifier types in the WS format to further reduce allocation.

[bfops]

Changes in my code-owned files LGTM