AK: Implement Stream::format(fmtstr, args...)

Based on `out()` and `vout()` from AK/Format.h. As opposed to those,
this propagates errors.

As `Core::File` extends `AK::Stream`, this allows formatted
printing directly on `Core::File`s.

AK/Stream.cpp

@@ -8,6 +8,7 @@
 #include <AK/ByteBuffer.h>
 #include <AK/Format.h>
 #include <AK/Stream.h>
+#include <AK/StringBuilder.h>
 
 namespace AK {
 
@@ -97,6 +98,16 @@ ErrorOr<void> Stream::write_until_depleted(ReadonlyBytes buffer)
     return {};
 }
 
+ErrorOr<void> Stream::format_impl(StringView fmtstr, TypeErasedFormatParams& parameters)
+{
+    StringBuilder builder;
+    TRY(vformat(builder, fmtstr, parameters));
+
+    auto const string = builder.string_view();
+    TRY(write_until_depleted(string.bytes()));
+    return {};
+}
+
 ErrorOr<size_t> SeekableStream::tell() const
 {
     // Seek with 0 and SEEK_CUR does not modify anything despite the const_cast,