starknet_patricia_storage: add as_gatherable_storage to storage trait

[nimrod-starkware]

Note

Medium Risk
Introduces a new method on the core Storage trait and updates multiple backends/wrappers to implement it, which is a public API change that can cause downstream compile breaks. Runtime behavior is largely unchanged but trait-bound tightening ('static/ImmutableReadOnlyStorage) may restrict some generic usages.

Overview
Adds Storage::as_gatherable_storage to optionally downcast a mutable Storage into a GatherableStorage for running concurrent read tasks.

Updates AerospikeStorage, MdbxStorage, RocksDbStorage, NullStorage, and CachedStorage to return Some(self) and implement/propagate GatherableStorage, and tightens CachedStorage (and CLI CachedStorageArgs) generic bounds to require ImmutableReadOnlyStorage + 'static.

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[reviewable-StarkWare]

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[nimrod-starkware]

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This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite.
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• starknet_committer: create storage tries concurrently based on wether storage is gatherable #13634
• starknet_patricia_storage: add as_gatherable_storage to storage trait #13633 👈 (View in Graphite)
• starknet_committer: create storage tries concurrently #13632
• starknet_patricia_storage: cache reads with gatherable storage #13631
• starknet_patricia_storage: define gatherable storage trait #13630
• starknet_patricia_storage: define storage task trait #13629
• starknet_committer: util for single storage trie creation #13358 : 1 other dependent PR (#13359 )
• starknet_committer: create sotrage tries sequentially #12166 : 1 other dependent PR (#12167 )
• starknet_patricia_storage: remove code dup for mget #12175 : 1 other dependent PR (#12201 )
• starknet_patricia_storage: spawn a task or not based on config #12174
• starknet_patricia_storage: add config field to rocksDB storage #12173
• starknet_patricia_storage: add config field to rocksDB #12172
• starknet_patricia_storage: spawn blocking tasks for rocksDB reads #12168 : 1 other dependent PR (#12169 )
• starknet_patricia_storage: always cache writes in cached storage #12443 : 2 other dependent PRs (#12444 , #13357 )
• starknet_patricia_storage: define reads collector storage #13240 : 1 other dependent PR (#13354 )
• starknet_patricia_storage: immutable read for cached storage #13237 : 1 other dependent PR (#13238 )
• starknet_patricia_storage: atomic counters for read stats #12122 : 1 other dependent PR (#12251 )
• starknet_patricia_storage: introduce immutable read only storage #13236
• starknet_committer: use read only storage if possible #13235
• starknet_patricia_storage: rename mutable getters #13379
• starknet_patricia_storage: split storage trait #13234
• main

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