refactor(threepid): Use SyncMutex and decouple guard from ValidSession

Change threepid sessions and send_attempts to SyncMutex and avoid

holding the sessions mutex across callers of get_valid_session.

src/web/pages/account/email.rs

@@ -167,7 +167,6 @@ async fn get_change_email_validate(
 	let Ok(session) = services
 		.threepid
 		.get_valid_session(&session_id, &client_secret)
-		.await
 	else {
 		return response!(ChangeEmailValidate::new(
 			context,

src/web/pages/account/password/reset.rs

@@ -189,7 +189,6 @@ async fn route_reset_password_validate(
 	let body = match services
 		.threepid
 		.get_valid_session(&query.threepid.session_id, &query.threepid.client_secret)
-		.await
 	{
 		| Ok(session) => {
 			let Some(localpart) = services

src/web/pages/account/register.rs

@@ -289,7 +289,6 @@ async fn get_register_email_validate(
 	let Ok(session) = services
 		.threepid
 		.get_valid_session(&session_id, &client_secret)
-		.await
 	else {
 		return response!(RegisterEmailValidate::new(context, session_id, client_secret, true));
 	};

src/web/pages/threepid.rs

@@ -33,7 +33,6 @@ async fn threepid_validation(
 	services
 		.threepid
 		.try_validate_session(&query.session, &query.token)
-		.await
 		.map_err(|message| WebError::BadRequest(message.into_owned()))?;
 
 	Ok(ThreepidValidation::new(context))