Change notification permission handling (#15176)

* Change notification permission handling

- allow changing individual alert settings even if permission is not explicitly
  enabled (asks for permission on toggle)
- persist permission request banner dismissal across sessions through settings

* Add additional, more discrete message to grant permissions

* Change permission granting button design according to reviews

Co-authored-by: Claire <claire.github-309c@sitedethib.com>

app/javascript/mastodon/features/notifications/components/grant_permission_button.js

@@ -0,0 +1,19 @@
+import React from 'react';
+import PropTypes from 'prop-types';
+import { FormattedMessage } from 'react-intl';
+
+export default class GrantPermissionButton extends React.PureComponent {
+
+  static propTypes = {
+    onClick: PropTypes.func.isRequired,
+  };
+
+  render () {
+    return (
+      <button className='text-btn column-header__permission-btn' tabIndex='0' onClick={this.props.onClick}>
+        <FormattedMessage id='notifications.grant_permission' defaultMessage='Grant permission.' />
+      </button>
+    );
+  }
+
+}