treewide: replace lock_guard with scoped_lock

SonarLint reports the latter to be better:

std::scoped_lock basically provides the same feature as std::lock_guard,
but is more generic: It can lock several mutexes at the same time, with a
deadlock prevention mechanism (see {rule:cpp:S5524}). The equivalent code
to perform simultaneous locking with std::lock_guard is significantly more
complex. Therefore, it is simpler to use std::scoped_lock all the time,
even when locking only one mutex (there will be no performance impact).

Signed-off-by: Rosen Penev <rosenp@gmail.com>

src/lib/smbclient/Context.cxx

@@ -45,7 +45,7 @@ SmbclientContext::New()
 	SMBCCTX *ctx;
 
 	{
-		const std::lock_guard<Mutex> protect(global_mutex);
+		const std::scoped_lock<Mutex> protect(global_mutex);
 		ctx = smbc_new_context();
 	}
 

src/lib/smbclient/Context.hxx

@@ -48,7 +48,7 @@ public:
 
 	~SmbclientContext() noexcept {
 		if (ctx != nullptr) {
-			const std::lock_guard<Mutex> protect(global_mutex);
+			const std::scoped_lock<Mutex> protect(global_mutex);
 			smbc_free_context(ctx, 1);
 		}
 	}