MM-21285: Remove environment overrides before config broadcast (#13527)

While sending the config broadcast message across a cluster, we would
include the environment overrides in the config.

We fix this by exposing a config config store method to remove the overrides,
and then calling that before saving the config across the cluster.

Co-authored-by: mattermod <mattermod@users.noreply.github.com>

config/store.go

@@ -20,6 +20,10 @@ type Store interface {
 	// GetEnvironmentOverrides fetches the configuration fields overridden by environment variables.
 	GetEnvironmentOverrides() map[string]interface{}
 
+	// RemoveEnvironmentOverrides returns a new config without the environment
+	// overrides
+	RemoveEnvironmentOverrides(cfg *model.Config) *model.Config
+
 	// Set replaces the current configuration in its entirety and updates the backing store.
 	Set(*model.Config) (*model.Config, error)