RPC server: io_uring upgrade

Separates the server into two parts: the context, and the work pool;
the context contains everything generally needed to run the server,
the work pool contains a statically polymorphic implementation for
a pool to dispatch the actual work to.
In doing this, we also separate certain things out into a few different
files.
The RPC server context API has been modified slightly to reflect this,
and the work pool directly exposed, for now.

src/accountsdb/db.zig

@@ -3390,6 +3390,7 @@ test "testWriteSnapshot" {
     );
 }
 
+/// Unpacks the snapshots from `sig.TEST_DATA_DIR`.
 pub fn findAndUnpackTestSnapshots(
     n_threads: usize,
     /// The directory into which the snapshots are unpacked.

src/accountsdb/snapshots.zig

@@ -2225,7 +2225,7 @@ pub const FullSnapshotFileInfo = struct {
     slot: Slot,
     hash: Hash,
 
-    const SnapshotArchiveNameFmtSpec = sig.utils.fmt.BoundedSpec("snapshot-{[slot]d}-{[hash]s}.tar.zst");
+    pub const SnapshotArchiveNameFmtSpec = sig.utils.fmt.BoundedSpec("snapshot-{[slot]d}-{[hash]s}.tar.zst");
 
     pub const SnapshotArchiveNameStr = SnapshotArchiveNameFmtSpec.BoundedArrayValue(.{
         .slot = std.math.maxInt(Slot),
@@ -2352,7 +2352,7 @@ pub const IncrementalSnapshotFileInfo = struct {
         };
     }
 
-    const SnapshotArchiveNameFmtSpec = sig.utils.fmt.BoundedSpec("incremental-snapshot-{[base_slot]d}-{[slot]d}-{[hash]s}.tar.zst");
+    pub const SnapshotArchiveNameFmtSpec = sig.utils.fmt.BoundedSpec("incremental-snapshot-{[base_slot]d}-{[slot]d}-{[hash]s}.tar.zst");
 
     pub const SnapshotArchiveNameStr = SnapshotArchiveNameFmtSpec.BoundedArrayValue(.{
         .base_slot = std.math.maxInt(Slot),
@@ -2498,15 +2498,16 @@ pub const SnapshotFiles = struct {
     full: FullSnapshotFileInfo,
     incremental_info: ?SlotAndHash,
 
-    pub fn incremental(snapshot_files: SnapshotFiles) ?IncrementalSnapshotFileInfo {
-        const inc_info = snapshot_files.incremental_info orelse return null;
+    pub fn incremental(self: SnapshotFiles) ?IncrementalSnapshotFileInfo {
+        const inc_info = self.incremental_info orelse return null;
         return .{
-            .base_slot = snapshot_files.full.slot,
+            .base_slot = self.full.slot,
             .slot = inc_info.slot,
             .hash = inc_info.hash,
         };
     }
 
+    /// Asserts that `if (maybe_incremental_info) |inc| inc.base_slot == full_info.slot`.
     pub fn fromFileInfos(
         full_info: FullSnapshotFileInfo,
         maybe_incremental_info: ?IncrementalSnapshotFileInfo,

src/rpc/lib.zig

@@ -6,7 +6,6 @@ pub const response = @import("response.zig");
 pub const types = @import("types.zig");
 
 pub const Client = client.Client;
-pub const Server = server.Server;
 
 pub const Request = request.Request;
 pub const Response = response.Response;