Update documentation for SafeMode and TxPause Pallets (#2413)

# Description

Documentation for the TxPause and SafeMode pallets.

Based on reading and the notes from the following related PRs:
- https://github.com/paritytech/substrate/pull/12092

I believe this also completes the checklist to be able to close the
related PRs:
- Close #302 
- Close #274

---------

Co-authored-by: joe petrowski <25483142+joepetrowski@users.noreply.github.com>

substrate/frame/safe-mode/src/tests.rs

@@ -189,6 +189,7 @@ fn can_filter_balance_in_proxy_when_activated() {
 	});
 }
 
+#[docify::export]
 #[test]
 fn can_activate() {
 	new_test_ext().execute_with(|| {
@@ -271,6 +272,7 @@ fn fails_force_deactivate_if_not_activated() {
 	});
 }
 
+#[docify::export]
 #[test]
 fn can_force_activate_with_config_origin() {
 	new_test_ext().execute_with(|| {
@@ -288,6 +290,7 @@ fn can_force_activate_with_config_origin() {
 	});
 }
 
+#[docify::export]
 #[test]
 fn can_force_deactivate_with_config_origin() {
 	new_test_ext().execute_with(|| {