Add support for type signatures in CEL environment YAML configuration.

The `env_yaml` parser now accepts type signatures for variable types and function overload signatures. The `type` field can be used instead of `type_name` for variables, allowing a more compact representation of types, including type parameters and parameterized types. The `signature` field can be used for function overloads, providing a single string to define the overload's target, arguments, and member status. The `return` type in function overloads can now also be specified as a type signature string.

PiperOrigin-RevId: 928959415

Author: dmitriplotnikov

env/BUILD

@@ -28,6 +28,7 @@ cc_library(
         "type_info.h",
     ],
     deps = [
+        "//common:ast",
         "//common:constant",
         "//common:type",
         "//common:type_kind",
@@ -120,7 +121,9 @@ cc_library(
     features = ["-use_header_modules"],
     deps = [
         ":config",
+        "//common:ast",
         "//common:constant",
+        "//common/internal:signature",
         "//internal:status_macros",
         "//internal:strings",
         "@com_google_absl//absl/algorithm:container",
@@ -178,9 +181,11 @@ cc_test(
         ":config",
         "//common:type",
         "//common:type_proto",
+        "//common/ast:metadata",
         "//internal:proto_matchers",
         "//internal:testing",
         "//internal:testing_descriptor_pool",
+        "@com_google_absl//absl/status",
         "@com_google_protobuf//:protobuf",
     ],
 )
@@ -201,7 +206,6 @@ cc_test(
         "//common:type",
         "//common:value",
         "//compiler",
-        "//internal:proto_matchers",
         "//internal:status_macros",
         "//internal:testing",
         "//internal:testing_descriptor_pool",
@@ -241,7 +245,6 @@ cc_test(
         "//common:value",
         "//compiler",
         "//extensions:math_ext",
-        "//internal:status_macros",
         "//internal:testing",
         "//internal:testing_descriptor_pool",
         "//runtime",