LibRegex: Use ReadonlySpan to peek into OpCode_Compare LUTs

By the time we're executing bytecode, we know the the bytecode will be
flattened. This means we can use ReadonlySpan to look into it instead of
DisjointChunks::spans(), which allocates.

AK/DisjointChunks.h

@@ -357,6 +357,12 @@ public:
         return true;
     }
 
+    [[nodiscard]] ReadonlySpan<T> flat_data() const
+    {
+        VERIFY(m_chunks.size() <= 1);
+        return m_chunks.is_empty() ? ReadonlySpan<T> {} : m_chunks.first().span();
+    }
+
     DisjointChunks release_slice(size_t start, size_t length) & { return move(*this).slice(start, length); }
     DisjointChunks release_slice(size_t start) & { return move(*this).slice(start); }
 

Libraries/LibRegex/RegexByteCode.cpp

@@ -540,7 +540,7 @@ ALWAYS_INLINE ExecutionResult OpCode_Compare::execute(MatchInput const& input, M
                 return ExecutionResult::Failed_ExecuteLowPrioForks;
 
             auto count = m_bytecode->at(offset++);
-            auto range_data = m_bytecode->template spans<4>().slice(offset, count);
+            auto range_data = m_bytecode->flat_data().slice(offset, count);
             offset += count;
 
             auto ch = input.view[state.string_position_in_code_units];