Syncing the async and sync API

[LDeakin]

The async API is still marked experimental and is lagging behind the sync API in a few areas.

API

• Add array_sharded_ext::{AsyncArrayShardedExt,AsyncArrayShardedReadableExt} etc
• Async support for StorageValueIO to enable ZipStorageAdapter with async stores or use an async zip crate
• Async support for partial encoding
• ... probably more

Performance

io_uring

It would be nice to have an io_uring backed filesystem store before digging into async performance profiling.

• Write efficiency: direct I/O? #53
• Tracking issues of Completion Based IO apache/opendal#4520

Async Tasks

The async API is less performant than the sync API, and I've not invested much time optimising it. One reason is that there is no internal task spawning. I've not added this mainly because it is a bit of a hassle while still keeping the crate async runtime agnostic. Also, I was hoping that async Rust would be further along in 2024 (async closures, keyword generics, async iterators, async traits with dynamic dispatch, structured concurrency, etc.). 2025 is looking better for async Rust.

Async Partial Decoders

If async tasks get sorted, a good follow-up would be to optimise the async partial decoders (particularly sharding).