script: nexantic -> monogon

This replaces the 'nexantic' build container with one called 'monogon'.

Also drive-by fix Fietsje's proto package path.

Test Plan: Refactor, CI only.

X-Origin-Diff: phab/D687
GitOrigin-RevId: 15165f3b57927836dc9601454b31dce4b2c09c7d
diff --git a/scripts/destroy_container.sh b/scripts/destroy_container.sh
index c60800a..750c829 100755
--- a/scripts/destroy_container.sh
+++ b/scripts/destroy_container.sh
@@ -1,4 +1,8 @@
 #!/bin/bash
 
-podman pod stop nexantic
-podman pod rm nexantic --force
+# TODO(by 2021/02/01): remove this (backward compatibility for dev envs)
+! podman pod stop nexantic
+! podman pod rm nexantic --force
+
+podman pod stop monogon
+podman pod rm monogon --force