Document dynamic email settings in Watcher

With this commit we document which of the email notification settings in
Watcher can be set dynamically via the cluster settings API.

Relates #36543

docs/reference/settings/notification-settings.asciidoc

@@ -14,7 +14,8 @@ You configure {watcher} settings to set up {watcher} and send notifications via
 All of these settings can be added to the `elasticsearch.yml` configuration file,
 with the exception of the secure settings, which you add to the {es} keystore.
 For more information about creating and updating the {es} keystore, see
-<<secure-settings>>.
+<<secure-settings>>. Dynamic settings can also be updated across a cluster with the
+<<cluster-update-settings,cluster update settings API>>.
 
 [float]
 [[general-notification-settings]]
@@ -83,69 +84,69 @@ Specifies account information for sending notifications via email. You
 can specify the following email account attributes:
 
 [[email-account-attributes]]
-  `profile`;;
+  `profile` (<<cluster-update-settings,Dynamic>>);;
   The {xpack-ref}/actions-email.html#configuring-email[email profile] to use to build the MIME
   messages that are sent from the account. Valid values: `standard`, `gmail` and
   `outlook`. Defaults to `standard`.
 
-  `email_defaults.*`;;
+  `email_defaults.*` (<<cluster-update-settings,Dynamic>>);;
   An optional set of email attributes to use as defaults
   for the emails sent from the account. See {xpack-ref}/actions-email.html#email-action-attributes[
   Email Action Attributes] for the supported attributes.
 
-  `smtp.auth`;;
+  `smtp.auth` (<<cluster-update-settings,Dynamic>>);;
   Set to `true` to attempt to authenticate the user using the
   AUTH command. Defaults to `false`.
 
-  `smtp.host`;;
+  `smtp.host` (<<cluster-update-settings,Dynamic>>);;
   The SMTP server to connect to. Required.
 
-  `smtp.port`;;
+  `smtp.port` (<<cluster-update-settings,Dynamic>>);;
   The SMTP server port to connect to. Defaults to 25.
 
-  `smtp.user`;;
+  `smtp.user` (<<cluster-update-settings,Dynamic>>);;
   The user name for SMTP. Required.
 
-  `smtp.password`;;
+  `smtp.password` (<<cluster-update-settings,Dynamic>>);;
   The password for the specified SMTP user.
 
-  `smtp.starttls.enable`;;
+  `smtp.starttls.enable` (<<cluster-update-settings,Dynamic>>);;
   Set to `true` to enable the use of the `STARTTLS`
   command (if supported by the server) to switch the connection to a
   TLS-protected connection before issuing any login commands. Note that
   an appropriate trust store must configured so that the client will
   trust the server's certificate. Defaults to `false`.
 
-  `smtp.starttls.required`;;
+  `smtp.starttls.required` (<<cluster-update-settings,Dynamic>>);;
   If `true`, then `STARTTLS` will be required. If that command fails, the
   connection will fail. Defaults to `false`.
 
-  `smtp.ssl.trust`;;
+  `smtp.ssl.trust` (<<cluster-update-settings,Dynamic>>);;
   A list of SMTP server hosts that are assumed trusted and for which
   certificate verification is disabled. If set to "*", all hosts are
   trusted. If set to a whitespace separated list of hosts, those hosts
   are trusted. Otherwise, trust depends on the certificate the server
   presents.
 
-  `smtp.timeout`;;
+  `smtp.timeout` (<<cluster-update-settings,Dynamic>>);;
   The socket read timeout. Default is two minutes.
 
-  `smtp.connection_timeout`;;
+  `smtp.connection_timeout` (<<cluster-update-settings,Dynamic>>);;
   The socket connection timeout. Default is two minutes.
 
-  `smtp.write_timeout`;;
+  `smtp.write_timeout` (<<cluster-update-settings,Dynamic>>);;
   The socket write timeout. Default is two minutes.
 
-  `smtp.local_address`;;
+  `smtp.local_address` (<<cluster-update-settings,Dynamic>>);;
   A configurable local address when sending emails. Not configured by default.
 
-  `smtp.local_port`;;
+  `smtp.local_port` (<<cluster-update-settings,Dynamic>>);;
   A configurable local port when sending emails. Not configured by default.
 
-  `smtp.send_partial`;;
+  `smtp.send_partial` (<<cluster-update-settings,Dynamic>>);;
   Send an email, despite one of the receiver addresses being invalid.
 
-  `smtp.wait_on_quit`;;
+  `smtp.wait_on_quit` (<<cluster-update-settings,Dynamic>>);;
   If set to false the QUIT command is sent and the connection closed. If set to
   true, the QUIT command is sent and a reply is waited for. True by default.