tools: manage mockery version using tools.go pattern

scripts/mockery_generate.sh

@@ -1,15 +1,6 @@
 #!/bin/sh
 #
 # Invoke Mockery v2 to update generated mocks for the given type.
-#
-# This script runs a locally-installed "mockery" if available, otherwise it
-# runs the published Docker container. This legerdemain is so that the CI build
-# and a local build can work off the same script.
-#
-if ! which mockery ; then
-  mockery() {
-    docker run --rm -v "$PWD":/w --workdir=/w vektra/mockery:v2.12.3
-  }
-fi
 
-mockery --disable-version-string --case underscore --name "$@"
+go run github.com/vektra/mockery/v2 --disable-version-string --case underscore --name "$*"
+