refactor(meta-embedded): remove embedded meta-store (#17888)

Replace embedded testing meta-service with standalone process.

The `MemMeta` and `MemStateMachine` implementations were previously used
for providing an embedded version of `databend-meta` service for testing.
This approach required maintaining two separate versions of meta-service,
creating long-term maintenance overhead.

Testing now uses a standalone databend-meta process running on a random
port and temporary directory. This change unifies our meta-service
implementation and eliminates the duplicated maintenance burden.

Author: drmingdrmer

Cargo.lock

@@ -97,7 +97,6 @@ members = [
     "src/meta/client",
     "src/meta/control",
     "src/meta/ee",
-    "src/meta/embedded",
     "src/meta/kvapi",
     "src/meta/process",
     "src/meta/proto-conv",
@@ -146,7 +145,6 @@ databend-common-meta-app-types = { path = "src/meta/app-types" }
 databend-common-meta-cache = { path = "src/meta/cache" }
 databend-common-meta-client = { path = "src/meta/client" }
 databend-common-meta-control = { path = "src/meta/control" }
-databend-common-meta-embedded = { path = "src/meta/embedded" }
 databend-common-meta-kvapi = { path = "src/meta/kvapi" }
 databend-common-meta-process = { path = "src/meta/process" }
 databend-common-meta-raft-store = { path = "src/meta/raft-store" }

Cargo.toml

@@ -23,8 +23,6 @@ pub mod config;
 pub mod key_spaces;
 pub mod leveled_store;
 pub(crate) mod marked;
-pub mod mem_meta;
-pub mod mem_state_machine;
 pub mod ondisk;
 pub mod raft_log_v004;
 pub mod sm_v003;