feat: address_state module

[whankinsiv]

This PR enables optional indexing of address-related data required for conformance with the Blockfrost API specification.

Storage lifecycle:

• The module subscribes to address deltas messages emitted by the UTxO state and applies them to the in-memory volatile layer which tracks live address updates within the rollback window.
• When the chain advances far enough that an entire previous epoch of deltas can no longer be rolled back, those finalized blocks are pruned from volatile and transferred into a pending queue within the ImmutableAddressStore.
• A background persistence worker consumes the epoch's pending deltas and atomically writes the updated immutable state to disk. Epochs are processed sequentially, with only one allowed in the queue before blocking the main run loop to prevent unbounded memory growth.

Retrieving live state:

• The immutable address data is first fetched from Fjall, and any pending immutable entries waiting to be persisted are merged into the result.
• The getter then iterates through each block in the in-memory volatile layer, applying any deltas relevant to the queried address on top of the immutable snapshot to produce an up-to-date view of the address state.

Data indexed:

pub struct AddressEntry {
    // The live utxo set for an address
    pub utxos: Option<Vec<UtxoDelta>>,      
        
    // All transactions involving the address
    pub transactions: Option<Vec<TxIdentifier>>, 

    // The total sent/received amounts for the address (lovelace + native assets)
    pub totals: Option<Vec<ValueDelta>>,            
}

REST handlers:

• This PR introduces the REST handler for the /addresses/{address} endpoint.
• A follow-up PR will add the /addresses/{address}/totals, /addresses/{address}/utxos, and /addresses/{address}/transactions endpoints, all of which rely on the data indexed by this module.

Next steps:

• Beyond implementing the remaining address-related REST handlers, refactoring the assets_state module to adopt the same storage lifecycle will significantly reduce the RAM footprint for address and transaction indexing.

[lowhung]

Very nicely done Will!

[lowhung]

I know these are fairly straightforward methods, but would it be worth adding to/creating tests to cover them?

[whankinsiv]

Tests for both script and normal addresses to stake_address_string added in a1767e6.

[lowhung]

More of a nit, but I do appreciate the /path this handle method corresponds to above this as a comment.

[whankinsiv]

Added comments above all address related handlers to indicate which endpoints they cover in 3dfa776.

[golddydev]

Should we limit the batch chunk by chunk, otherwise it ends up batching tons of data which is not that efficient.

[whankinsiv]

I decided to do it this way so that if the program is exited or crashes mid persistence we wont have a corrupted DB. I'm open to any alternative solutions you may have.