datastore: apply schema changes immediately to committed state.

[Centril]

Description of Changes

TODO

API and ABI breaking changes

None

Expected complexity level and risk

4, this is isolated to the datastore, but the datastore is critical, subtle, and contains various unsafe.

Testing

TODO

[Copilot]

Pull Request Overview

This PR introduces immediate application of schema changes to the committed datastore state and updates various index and schema manipulation APIs. Key changes include the addition of new merging functions (can_merge) for several index types, revised schema mutation and index deletion APIs in Table, and significant restructuring of transaction state and rollback mechanisms in the core datastore layer.

Reviewed Changes

Copilot reviewed 14 out of 14 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
crates/table/src/table_index/uniquemap.rs	Added a can_merge method to verify if two UniqueMaps can be merged
crates/table/src/table_index/unique_direct_index.rs	Added a can_merge method for unique direct indices using a zip iteration over inner collections
crates/table/src/table_index/unique_direct_fixed_cap_index.rs	Added a can_merge function to similar effect for fixed capacity indices
crates/table/src/table_index/mod.rs	Introduced a could_merge method for TableIndex that dispatches to the appropriate can_merge functions
crates/table/src/table.rs	Modified schema mutation functions and index add/delete operations with updated pointer map handling
crates/schema/src/schema.rs	Revised adjacent schema modifications using a new take_adjacent_schemas API and helper find_remove
crates/core/src/db/datastore/locking_tx_datastore/*	Updated transaction state and rollback handling to immediately reflect schema changes, plus various related API adjustments

Comments suppressed due to low confidence (3)

crates/table/src/table_index/uniquemap.rs:87

• Add unit tests for the new can_merge method to verify its behavior when merging maps that have conflicting keys as well as when no conflicts are present.

pub(crate) fn can_merge(&self, other: &UniqueMap<K, V>) -> Result<(), &V> {

crates/table/src/table_index/unique_direct_index.rs:210

• Ensure that unit tests are added for can_merge to cover scenarios where inner slot conflicts occur and where merge should succeed without errors.

pub(crate) fn can_merge(&self, other: &UniqueDirectIndex) -> Result<(), RowPointer> {

crates/table/src/table_index/unique_direct_fixed_cap_index.rs:126

• Introduce tests for the new can_merge function to confirm that the function correctly identifies merge conflicts when both slots are occupied.

pub(crate) fn can_merge(&self, other: &UniqueDirectFixedCapIndex) -> Result<(), RowPointer> {

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