refactor(planner): extract the Stage 3 plan-selection crate

Move asap-aware-mapping's Stage 3 modules into the new asap-plan-selection
crate: the cost model and its inputs under cost/, plan_selection/mod.rs as
the crate root (select_plan, PlanningModels) and candidate_selection, with
their tests and the test_support copy. Delete pane_sharing, erp and
empirical_comparison, which have no callers (#572), and the
snapshot_prepare_cpu helper only empirical_comparison used. A manifest
guard rejects the facade and executor. Imports are rewritten without
compatibility re-exports (#572, B4).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Author: zzylol

Cargo.lock

@@ -7,6 +7,7 @@ members = [
     "crates/asap-aware-mapping",
     "crates/logical-optimizer",
     "crates/physical-optimizer",
+    "crates/plan-selection",
     "crates/frontend-promql",
     "crates/frontend-metricsql",
     "crates/metricsql-common-parser-support",

Cargo.toml

@@ -3,16 +3,12 @@ name = "asap-aware-mapping"
 version = "0.1.0"
 edition = "2021"
 
-# #509 Stage 3 and the planner facade over the Stage 1 candidates of
-# asap-logical-optimizer and the Stage 2 candidates of asap-physical-optimizer.
+# The planner facade (pass/) over the #509 stage crates: Stage 1
+# asap-logical-optimizer and Stage 3 asap-plan-selection (which brings Stage 2).
 # Never depends on a front end.
 [dependencies]
 asap-types = { path = "../types" }
 asap-logical-optimizer = { path = "../logical-optimizer" }
-asap-physical-optimizer = { path = "../physical-optimizer" }
+asap-plan-selection = { path = "../plan-selection" }
 thiserror = "2"
-serde = { version = "1", features = ["derive"] }
-serde_json = "1"
 
-[dev-dependencies]
-asap-frontend-promql = { path = "../frontend-promql" }