Everywhere: Remove unintentional partial stream reads and writes

Author: https://github.com/timschumi
Commit: ae51c1821c
Pull-request: https://github.com/SerenityOS/serenity/pull/17684
Reviewed-by: https://github.com/JanDeVisser ✅
Reviewed-by: https://github.com/alimpfard
Reviewed-by: https://github.com/linusg ✅

Tests/LibWeb/TestHTMLTokenizer.cpp

@@ -211,8 +211,7 @@ TEST_CASE(regression)
     auto file = MUST(Core::File::open(path, Core::File::OpenMode::Read));
     auto file_size = MUST(file->size());
     auto content = MUST(ByteBuffer::create_uninitialized(file_size));
-    // FIXME: This should read the entire span.
-    MUST(file->read_some(content.bytes()));
+    MUST(file->read_until_filled(content.bytes()));
     DeprecatedString file_contents { content.bytes() };
     auto tokens = run_tokenizer(file_contents);
     u32 hash = hash_tokens(tokens);