server: introduce ServerMetricRecorder API and move per-call reportin…

…g from a C++ interceptor to a C-core filter (#32106)

* backend metric sampling

* Comments addressed.

* More comments addressed.

* Pushing changes left behind locally.

* Removed empty lines

* Update OrcaService to use ServerMetricRecorder (no named metrics yet)

* Comments addressed.

* More comments addressed

* More comments addressed.

* Comments fixed

* Comments addressed.

* Test fixed

* make seq returned always up-to-date

* skip atomic load when not cached

* Fixed ABSL_GUARDED_BY

* Comments addressed except client_lb_end2end_test

* test updated

* Comments addressed

* BUILD fix.

* BackendMetricDataState moved to a separate header

* comments addressed

* Fixed clang and buildifier errors

* More sanity check errors fixed.

* Fixed xds tests

* Ran generate_projects.sh

* Comments addressed

* comments addressed.

* generate project

* Build fixed

* generate project

* sanity check errors fixed

* test fixed

* Backup poller period override moved to main()

* Also move cfstream override

* Clang fixes, sanitize

* generate_projects.sh

* portable print format fix

* Removed outdated comment

BUILD

@@ -761,6 +761,7 @@ grpc_cc_library(
         "grpc_base",
         # standard plugins
         "census",
+        "//src/core:grpc_backend_metric_filter",
         "//src/core:grpc_deadline_filter",
         "//src/core:grpc_client_authority_filter",
         "//src/core:grpc_lb_policy_grpclb",
@@ -1818,6 +1819,7 @@ grpc_cc_library(
         "grpc_security_base",
         "grpc_service_config_impl",
         "grpc_trace",
+        "grpcpp_backend_metric_recorder",
         "grpcpp_call_metric_recorder",
         "grpcpp_status",
         "iomgr_timer",
@@ -1833,6 +1835,7 @@ grpc_cc_library(
         "//src/core:error",
         "//src/core:gpr_atm",
         "//src/core:gpr_manual_constructor",
+        "//src/core:grpc_backend_metric_provider",
         "//src/core:grpc_service_config",
         "//src/core:grpc_transport_inproc",
         "//src/core:json",
@@ -1885,6 +1888,7 @@ grpc_cc_library(
         "grpc_service_config_impl",
         "grpc_trace",
         "grpc_unsecure",
+        "grpcpp_backend_metric_recorder",
         "grpcpp_call_metric_recorder",
         "grpcpp_status",
         "iomgr_timer",
@@ -1896,6 +1900,7 @@ grpc_cc_library(
         "//src/core:error",
         "//src/core:gpr_atm",
         "//src/core:gpr_manual_constructor",
+        "//src/core:grpc_backend_metric_provider",
         "//src/core:grpc_insecure_credentials",
         "//src/core:grpc_service_config",
         "//src/core:grpc_transport_inproc",
@@ -1973,45 +1978,42 @@ grpc_cc_library(
 
 grpc_cc_library(
     name = "grpcpp_call_metric_recorder",
-    srcs = [
-        "src/cpp/server/orca/call_metric_recorder.cc",
-    ],
     external_deps = [
         "absl/strings",
         "absl/types:optional",
-        "upb_lib",
     ],
     language = "c++",
     public_hdrs = [
         "include/grpcpp/ext/call_metric_recorder.h",
     ],
     visibility = ["@grpc:public"],
-    deps = [
-        "grpc++_public_hdrs",
-        "xds_orca_upb",
-        "//src/core:arena",
-        "//src/core:grpc_backend_metric_data",
-    ],
+    deps = ["grpc++_public_hdrs"],
 )
 
 grpc_cc_library(
-    name = "grpcpp_orca_interceptor",
+    name = "grpcpp_backend_metric_recorder",
     srcs = [
-        "src/cpp/server/orca/orca_interceptor.cc",
+        "src/cpp/server/backend_metric_recorder.cc",
     ],
     hdrs = [
-        "src/cpp/server/orca/orca_interceptor.h",
+        "src/cpp/server/backend_metric_recorder.h",
     ],
     external_deps = [
+        "absl/base:core_headers",
         "absl/strings",
-        "absl/types:optional",
     ],
     language = "c++",
+    public_hdrs = [
+        "include/grpcpp/ext/server_metric_recorder.h",
+    ],
     visibility = ["@grpc:public"],
     deps = [
-        "grpc++",
-        "grpc_base",
+        "gpr",
+        "grpc++_public_hdrs",
+        "grpc_trace",
         "grpcpp_call_metric_recorder",
+        "//src/core:grpc_backend_metric_data",
+        "//src/core:grpc_backend_metric_provider",
     ],
 )
 
@@ -2022,6 +2024,7 @@ grpc_cc_library(
     ],
     external_deps = [
         "absl/base:core_headers",
+        "absl/strings",
         "absl/time",
         "absl/types:optional",
         "upb_lib",
@@ -2037,11 +2040,13 @@ grpc_cc_library(
         "gpr",
         "grpc++",
         "grpc_base",
+        "grpcpp_backend_metric_recorder",
         "protobuf_duration_upb",
         "ref_counted_ptr",
         "xds_orca_service_upb",
         "xds_orca_upb",
         "//src/core:default_event_engine",
+        "//src/core:grpc_backend_metric_data",
         "//src/core:ref_counted",
         "//src/core:time",
     ],