Adds "Fjall" as a DB backend for moor

Fjall is an LSM-based storage engine similar in some respects to
RocksDB, but written in pure Rust.

Depending on how this works out, this may become the default, and I
may retire the WiredTiger bindings, as it has become a source of
stress in compilation. And its isolation level is perhaps not high
enough.

Cargo.toml

@@ -5,6 +5,7 @@ members = [
     "crates/compiler",
     "crates/daemon",
     "crates/db",
+    "crates/db-fjall",
     "crates/db-relbox",
     "crates/db-wiredtiger",
     "crates/kernel",
@@ -133,6 +134,7 @@ thiserror = "2.0"
 paste = "1.0"
 
 # For the DB & values layer.
+fjall = { version = "2.3.2", default-features = false, features = ["ssi_tx", "bytes"] }
 libc = "0.2"
 relbox = { git = "https://github.com/rdaum/Relbox.git", version = "0.2.0" }
 text_io = "0.1" # Used for reading text dumps.

crates/daemon/Cargo.toml

@@ -16,6 +16,7 @@ moor-db-relbox = { path = "../db-relbox", optional = true }
 relbox = { workspace = true, optional = true }
 
 moor-db = { path = "../db" }
+moor-db-fjall = { path = "../db-fjall" }
 moor-db-wiredtiger = { path = "../db-wiredtiger" }
 moor-kernel = { path = "../kernel" }
 moor-values = { path = "../values" }
@@ -32,6 +33,7 @@ bytes.workspace = true
 color-eyre.workspace = true
 daumtils.workspace = true
 eyre.workspace = true
+fjall.workspace = true
 oneshot.workspace = true
 signal-hook.workspace = true
 tempfile.workspace = true