[cppcheck] convert several functions to use std::all_of

std::all_of becomes constexpr in C++20. I'm not sure it results in better
performance.

Found with useStlAlgorithm

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

src/output/MultipleOutputs.cxx

@@ -258,11 +258,8 @@ MultipleOutputs::Open(const AudioFormat audio_format)
 bool
 MultipleOutputs::IsChunkConsumed(const MusicChunk *chunk) const noexcept
 {
-	for (const auto &ao : outputs)
-		if (!ao->LockIsChunkConsumed(*chunk))
-			return false;
-
-	return true;
+	return std::all_of(outputs.begin(), outputs.end(), [chunk](const auto &ao) {
+		return ao->LockIsChunkConsumed(*chunk); });
 }
 
 unsigned

src/output/MultipleOutputs.hxx

@@ -28,6 +28,7 @@
 #include "Chrono.hxx"
 #include "util/Compiler.h"
 
+#include <algorithm>
 #include <cassert>
 #include <memory>
 #include <vector>
@@ -106,11 +107,7 @@ public:
 	 */
 	gcc_pure
 	bool IsDummy() const noexcept {
-		for (const auto &i : outputs)
-			if (!i->IsDummy())
-				return false;
-
-		return true;
+		return std::all_of(outputs.begin(), outputs.end(), [](const auto &i) { return i->IsDummy(); });
 	}
 
 	/**