feat: prw_v2 initial commit with sample ingestion (#8361)

* chore: add v2 entrance

Signed-off-by: shuiyisong <xixing.sys@gmail.com>

* chore: decode request

Signed-off-by: shuiyisong <xixing.sys@gmail.com>

* chore: implement remote write v2 for samples

Signed-off-by: shuiyisong <xixing.sys@gmail.com>

* chore: add tests

Signed-off-by: shuiyisong <xixing.sys@gmail.com>

* chore: remove hand-written proto

Signed-off-by: shuiyisong <xixing.sys@gmail.com>

* chore: refactor

Signed-off-by: shuiyisong <xixing.sys@gmail.com>

* fix: CR issue

Signed-off-by: shuiyisong <xixing.sys@gmail.com>

* fix: CR issue

Signed-off-by: shuiyisong <xixing.sys@gmail.com>

* fix: merge tests

Signed-off-by: shuiyisong <xixing.sys@gmail.com>

* chore: add source version field

Signed-off-by: shuiyisong <xixing.sys@gmail.com>

* chore: fix CR issues

Signed-off-by: shuiyisong <xixing.sys@gmail.com>

* fix: test

Signed-off-by: shuiyisong <xixing.sys@gmail.com>

* fix: sqlness

Signed-off-by: shuiyisong <xixing.sys@gmail.com>

* chore: update proto

Signed-off-by: shuiyisong <xixing.sys@gmail.com>

* chore: update proto

Signed-off-by: shuiyisong <xixing.sys@gmail.com>

---------

Signed-off-by: shuiyisong <xixing.sys@gmail.com>

docs/rfcs/2026-05-28-table-semantic-layer.md

@@ -67,6 +67,7 @@ concern, not query-time semantics).
 | --- | --- |
 | `greptime.semantic.signal_type` | `trace` / `log` / `metric` / `event` |
 | `greptime.semantic.source` | `opentelemetry` / `prometheus` / `influxdb` / `opentsdb` / `elasticsearch` / `loki` / `custom` |
+| `greptime.semantic.source_version` | Source protocol version, e.g. Prometheus remote write `1.0` / `2.0` |
 | `greptime.semantic.pipeline` | `greptime_trace_v1` (the signal-agnostic successor to `table_data_model`) |
 
 **Trace**: `greptime.semantic.trace.conventions` (the OTel `schema_url` the rows conform to, or `mixed` / `unknown` when not single-valued).
@@ -83,7 +84,7 @@ concern, not query-time semantics).
 
 `metadata_quality = inferred` is the load-bearing field for confidence-aware tooling: an inferred counter should be re-checked before betting on `rate()`-style semantics.
 
-**Deliberately omitted (and why)**: `metric.monotonic` (a function of `type`); `trace.has_events`/`has_links` (constant for the v1 model and derivable from the `span_events`/`span_links` columns); `log.severity_scheme`/`log.body_format` (constant / derivable by sampling, and the latter cost an O(rows) scan); `resource.attributes_preserved`/`attributes_dropped`/`scope.preserved` (the preserved set restates columns, the dropped flag is a contentless boolean, and lineage is a collector-config concern); `source_version` (no cheap non-constant value today — Prom RW is v1-only, OTel SDK identity is deferred). Some are reserved for follow-ups (see Future Work).
+**Deliberately omitted (and why)**: `metric.monotonic` (a function of `type`); `trace.has_events`/`has_links` (constant for the v1 model and derivable from the `span_events`/`span_links` columns); `log.severity_scheme`/`log.body_format` (constant / derivable by sampling, and the latter cost an O(rows) scan); `resource.attributes_preserved`/`attributes_dropped`/`scope.preserved` (the preserved set restates columns, the dropped flag is a contentless boolean, and lineage is a collector-config concern). Some are reserved for follow-ups (see Future Work).
 
 ## Conflict and update semantics