feat(rust/sedona-spatial-join) Add partitioned index provider

[Kontinuation]

This patch adds a index provider for coordinating the creation of spatial index for specified partitions. It is also integrated into SpatialJoinExec so we use it to create the spatial index even when there's only one spatial partition (the degenerate case). The handling for multiple spatial partitions will be added in a subsequent PR.

The memory reservations growed in the build side collection phase will be held by PartitionedIndexProvider. Spatial indexes created by the provider does not need to hold memory reservations.

The next step is to support partitioned probe side by adding a PartitionedProbeStreamProvider, and modify the state machine of SpatialJoinStream to process multiple spatial partitions sequentially.

[Copilot]

Pull request overview

This PR adds a PartitionedIndexProvider to coordinate the creation and caching of spatial indexes for specified partitions. The provider is integrated into SpatialJoinExec and SpatialJoinStream, replacing the previous direct spatial index building approach. Memory reservations from the build side collection phase are now held by the provider rather than individual indexes. This is a preparatory step for supporting multi-partitioned spatial joins.

Changes:

• Introduced PartitionedIndexProvider to manage index creation and caching across partitions
• Refactored SpatialJoinStream to use the provider for index access
• Moved memory reservation ownership from spatial indexes to the provider

Reviewed changes

Copilot reviewed 15 out of 15 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
rust/sedona-spatial-join/src/utils/disposable_async_cell.rs	New utility for async cell that can be disposed to avoid unnecessary memory usage
rust/sedona-spatial-join/src/utils/bbox_sampler.rs	Removed #![allow(unused)] attribute
rust/sedona-spatial-join/src/utils.rs	Added disposable_async_cell module
rust/sedona-spatial-join/src/stream.rs	Updated to use PartitionedIndexProvider for index creation
rust/sedona-spatial-join/src/prepare.rs	New module for preparing spatial join components including the provider
rust/sedona-spatial-join/src/lib.rs	Replaced build_index module with prepare module
rust/sedona-spatial-join/src/index/spatial_index_builder.rs	Removed memory reservation tracking from builder
rust/sedona-spatial-join/src/index/spatial_index.rs	Removed memory reservation field from SpatialIndex
rust/sedona-spatial-join/src/index/partitioned_index_provider.rs	New provider for managing partitioned spatial indexes
rust/sedona-spatial-join/src/index/memory_plan.rs	New module for computing memory usage plans
rust/sedona-spatial-join/src/index/build_side_collector.rs	Added accessor method for spill metrics
rust/sedona-spatial-join/src/index.rs	Added new modules to index module
rust/sedona-spatial-join/src/exec.rs	Updated to create and use PartitionedIndexProvider
rust/sedona-spatial-join/src/build_index.rs	Removed memory pool parameter from index builder
rust/sedona-spatial-join/Cargo.toml	Added tokio dependency

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