feat: meta-service: add proposed_at tracking the time when a key is written (#18812)

* feat: meta-service: add `proposed_at` tracking the time when a key is written

Add `proposed_at_ms` field to `KvMeta` protobuf to track proposal
timestamps for key-value operations in the meta service.

Introduce `ReduceSeqV` trait with two methods: `erase_proposed_at()`
removes timestamps from metadata for test comparisons, and `reduce()`
removes default-valued metadata to minimize storage overhead.

Implement the trait for common types including `SeqV<T>`,
`Option<SeqV<T>>`, collection types, and domain-specific types
(`Change`, `pb::Event`, `pb::StreamItem`). Update all meta service
tests to use `erase_proposed_at()` when comparing results, allowing
tests to ignore variable proposal timestamps while verifying data
correctness. Add comprehensive unit tests covering metadata erasure
and reduction behavior.

* refactor: update tests for KVMeta proposed_at_ms field

Fixed compilation errors and test assertions after adding proposed_at_ms
to KVMeta structure. Updated tests to handle the new field:

- Updated KVMeta::new() calls to include proposed_at_ms parameter
- Applied .erase_proposed_at() for SeqV types in assertions
- Updated expected values to match database default (Some(0))
- Replaced legacy KVMeta::new_expires_at() calls
- Updated JSON serialization test expectations

All 94 raft-store tests now passing.

* refactor: rename ReduceSeqV to NormalizeMeta with improved docs

* M  src/meta/service/tests/it/grpc/metasrv_grpc_kv_read_v1.rs

* M  tests/metactl/want_exported_v004

* M  src/meta/client/src/lib.rs

* M  tests/metactl/subcommands/cmd_export_from_grpc.py

Author: drmingdrmer

Cargo.lock

@@ -498,7 +498,7 @@ socket2 = "0.5.3"
 span-map = { version = "0.2.0" }
 sqlx = { version = "0.8", features = ["mysql", "runtime-tokio"] }
 state = "0.6.0"
-state-machine-api = { version = "0.3.1" }
+state-machine-api = { version = "0.3.4" }
 stream-more = "0.1.3"
 strength_reduce = "0.2.4"
 stringslice = "0.2.0"
@@ -663,7 +663,7 @@ openraft = { git = "https://github.com/databendlabs/openraft", tag = "v0.10.0-al
 orc-rust = { git = "https://github.com/datafuse-extras/orc-rust", rev = "d82aa6d" }
 recursive = { git = "https://github.com/datafuse-extras/recursive.git", rev = "16e433a" }
 sled = { git = "https://github.com/datafuse-extras/sled", tag = "v0.34.7-datafuse.1" }
-state-machine-api = { git = "https://github.com/databendlabs/state-machine-api.git", tag = "v0.3.1" }
+state-machine-api = { git = "https://github.com/databendlabs/state-machine-api.git", tag = "v0.3.4" }
 sub-cache = { git = "https://github.com/databendlabs/sub-cache", tag = "v0.2.1" }
 tantivy = { git = "https://github.com/datafuse-extras/tantivy", rev = "7502370" }
 tantivy-common = { git = "https://github.com/datafuse-extras/tantivy", rev = "7502370", package = "tantivy-common" }

Cargo.toml

@@ -155,6 +155,9 @@ use semver::Version;
 /// - 2025-09-27: since 1.2.821
 ///   👥 client: require 1.2.764(yanked), use 1.2.768, for `FetchAddU64`
 ///
+/// - 2025-09-30: since TODO
+///   🖥 server: store raft-log proposing time `proposed_at_ms` in `KVMeta`.
+///
 /// Server feature set:
 /// ```yaml
 /// server_features: