feat: introduce and configure node with tiered KVStore

Introduces TierStore, a KVStore implementation that manages data
across three storage layers:

- Primary: Main/remote data store
- Ephemeral: Secondary store for non-critical, easily-rebuildable
  data (e.g., network graph) with fast local access
- Backup: Tertiary store for disaster recovery with async/lazy
  operations to avoid blocking primary store

Adds four configuration methods to NodeBuilder:

- set_tier_store_backup: Configure backup data store
- set_tier_store_ephemeral: Configure ephemeral data store
- set_tier_store_retry_config: Configure retry parameters with
  exponential backoff
- build_with_tier_store: Build node with primary data store

These methods are exposed to the foreign interface via additions
in ffi/types.rs:

- ffi::SyncAndAsyncKVStore: Composed of KVStore and KVStoreSync
  methods to handle the types::SyncAndAsyncKVStore supertrait
  across FFI
- ffi::ForeignKVStoreAdapter and ffi::DynStore: Adapt/translate
  between foreign language store and native Rust store
- Conditional compilation for DynStore: ffi::DynStore with uniffi,
  types::DynStore without, with selection aided by the wrap_store!()
  macro

Author: enigbe

Cargo.toml

@@ -63,6 +63,7 @@ bitcoin = "0.32.7"
 bip39 = { version = "2.0.0", features = ["rand"] }
 bip21 = { version = "0.5", features = ["std"], default-features = false }
 
+async-trait = {version = "0.1.89"}
 base64 = { version = "0.22.1", default-features = false, features = ["std"] }
 rand = { version = "0.9.2", default-features = false, features = ["std", "thread_rng", "os_rng"] }
 chrono = { version = "0.4", default-features = false, features = ["clock"] }

bindings/ldk_node.udl

@@ -55,6 +55,12 @@ enum WordCount {
 	"Words24",
 };
 
+dictionary RetryConfig {
+	u16 initial_retry_delay_ms;
+	u16 maximum_delay_secs;
+	f32 backoff_multiplier;
+};
+
 enum LogLevel {
 	"Gossip",
 	"Trace",
@@ -76,6 +82,56 @@ interface LogWriter {
 	void log(LogRecord record);
 };
 
+interface DynStore {
+    [Name=from_store]
+    constructor(SyncAndAsyncKVStore store);
+};
+
+[Trait, WithForeign]
+interface SyncAndAsyncKVStore {
+    // KVStoreSync versions
+    [Throws=IOError]
+    sequence<u8> read_sync(string primary_namespace, string secondary_namespace, string key);
+    [Throws=IOError]
+    void write_sync(string primary_namespace, string secondary_namespace, string key, sequence<u8> buf);
+    [Throws=IOError]
+    void remove_sync(string primary_namespace, string secondary_namespace, string key, boolean lazy);
+    [Throws=IOError]
+    sequence<string> list_sync(string primary_namespace, string secondary_namespace);
+    
+    // KVStore versions
+    [Throws=IOError, Async]
+    sequence<u8> read_async(string primary_namespace, string secondary_namespace, string key);
+    [Throws=IOError, Async]
+    void write_async(string primary_namespace, string secondary_namespace, string key, sequence<u8> buf);
+    [Throws=IOError, Async]
+    void remove_async(string primary_namespace, string secondary_namespace, string key,  boolean lazy);
+    [Throws=IOError, Async]
+    sequence<string> list_async(string primary_namespace, string secondary_namespace);
+};
+
+[Error]
+enum IOError {
+  	"NotFound",
+    "PermissionDenied",
+    "ConnectionRefused",
+    "ConnectionReset",
+    "ConnectionAborted",
+    "NotConnected",
+    "AddrInUse",
+    "AddrNotAvailable",
+    "BrokenPipe",
+    "AlreadyExists",
+    "WouldBlock",
+    "InvalidInput",
+    "InvalidData",
+    "TimedOut",
+    "WriteZero",
+    "Interrupted",
+    "UnexpectedEof",
+    "Other",
+};
+
 interface Builder {
 	constructor();
 	[Name=from_config]
@@ -104,6 +160,9 @@ interface Builder {
 	void set_announcement_addresses(sequence<SocketAddress> announcement_addresses);
 	[Throws=BuildError]
 	void set_node_alias(string node_alias);
+	void set_tier_store_retry_config(RetryConfig retry_config);
+	void set_tier_store_backup(DynStore backup_store);
+	void set_tier_store_ephemeral(DynStore ephemeral_store);
 	[Throws=BuildError]
 	void set_async_payments_role(AsyncPaymentsRole? role);
 	[Throws=BuildError]
@@ -116,6 +175,8 @@ interface Builder {
 	Node build_with_vss_store_and_fixed_headers(string vss_url, string store_id, record<string, string> fixed_headers);
 	[Throws=BuildError]
 	Node build_with_vss_store_and_header_provider(string vss_url, string store_id, VssHeaderProvider header_provider);
+	[Throws=BuildError]
+	Node build_with_tier_store(DynStore primary_store);
 };
 
 interface Node {