Add the protobuf message and the selector API (#3797)

* Define the protobuf API for selectors

* Add the selector evalautor

Adds a new module called selectors that initializes CEL environments and
evaluates selectors.

Fixes: #3757

* Move converting entities to SelectorEntity structs to providers

* Support properties in selectors

* Change the selectors to google.protobuf.Struct

go.mod

@@ -22,6 +22,7 @@ require (
 	github.com/goccy/go-json v0.10.3
 	github.com/golang-jwt/jwt/v4 v4.5.0
 	github.com/golang-migrate/migrate/v4 v4.17.1
+	github.com/google/cel-go v0.20.1
 	github.com/google/go-cmp v0.6.0
 	github.com/google/go-containerregistry v0.20.1
 	github.com/google/go-github/v63 v63.0.0
@@ -119,7 +120,6 @@ require (
 	github.com/go-sql-driver/mysql v1.8.1 // indirect
 	github.com/gogo/protobuf v1.3.2 // indirect
 	github.com/golang-jwt/jwt/v5 v5.2.1 // indirect
-	github.com/google/cel-go v0.20.1 // indirect
 	github.com/google/go-github/v61 v61.0.0 // indirect
 	github.com/grpc-ecosystem/go-grpc-middleware v1.4.0 // indirect
 	github.com/hashicorp/go-sockaddr v1.0.5 // indirect