SQL: Allow skip of bwc tests on `check` task (#62936)

Bwc tests can consume much time to build and to run so it's nice to be
able to skip them when running the `check` task on the SQL module.

Introduce a new task `checkNoBwc` so one can use:
```
./gradlew -p x-pack/plugin/sql checkNoBwc
```
to skip them.

x-pack/plugin/sql/build.gradle

@@ -132,3 +132,9 @@ tasks.register("regen") {
     }
   }
 }
+
+allprojects {
+  task checkNoBwc {
+    dependsOn tasks.withType(Test).matching { it.name.contains('bwc') == false }
+  }
+}