[llvm] [CodeGen] Derive the regalloc pipeline from the allocator, remove -optimize-regalloc (PR #215740)

[Fangrui Song via llvm-commits]

MaskRay wrote:

Formatted CodeGenPassBuilder.h,  but I disagree with the `TargetPassConfig.cpp` suggestion.The patch deletes lines from the file, and it should not be forced to format unrelated neighbor lines.

```
--- a/llvm/lib/CodeGen/TargetPassConfig.cpp
+++ b/llvm/lib/CodeGen/TargetPassConfig.cpp
@@ -81,7 +81,8 @@ static cl::opt<bool> DisableEarlyIfConversion("disable-early-ifcvt", cl::Hidden,
     cl::desc("Disable Early If-conversion"));
 static cl::opt<bool> DisableMachineLICM("disable-machine-licm", cl::Hidden,
     cl::desc("Disable Machine LICM"));
-static cl::opt<bool> DisableMachineCSE("disable-machine-cse", cl::Hidden,
+static cl::opt<bool> DisableMachineCSE(
+    "disable-machine-cse", cl::Hidden,
     cl::desc("Disable Machine Common Subexpression Elimination"));
 static cl::opt<bool> DisablePostRAMachineLICM("disable-postra-machine-licm",
     cl::Hidden,
```

https://github.com/llvm/llvm-project/pull/215740