[llvm] [NFC][RA] Refactor RABasic into a Separate Header (PR #149555)

[Matthias Braun via llvm-commits]

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@@ -0,0 +1,107 @@
+//===-- RegAllocBasic.h - Basic Register Allocator Header -----------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file declares the RABasic class, which provides a minimal
+// implementation of the basic register allocator.
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MatzeB wrote:

use syntax recognized by doxygen (and possibly fix the pre-existing problem in RegAllocBasic.cpp)
```suggestion
/// \file This file declares the RABasic class, which provides a minimal
/// implementation of the basic register allocator.
```

https://github.com/llvm/llvm-project/pull/149555