Re-apply '[AArch64] Enable "sink-and-fold" in MachineSink by default (#67432)'

This re-applies commit a9d0ab2, which
was reverted by 8abb2ac.

The issue was fixed by 7510f32

Author: momchil-velikov

llvm/lib/Target/AArch64/AArch64TargetMachine.cpp

@@ -200,7 +200,7 @@ static cl::opt<bool> EnableGISelLoadStoreOptPostLegal(
 static cl::opt<bool>
     EnableSinkFold("aarch64-enable-sink-fold",
                    cl::desc("Enable sinking and folding of instruction copies"),
-                   cl::init(false), cl::Hidden);
+                   cl::init(true), cl::Hidden);
 
 extern "C" LLVM_EXTERNAL_VISIBILITY void LLVMInitializeAArch64Target() {
   // Register the target.

llvm/test/CodeGen/AArch64/machine-sink-cache-invalidation.ll

@@ -22,8 +22,7 @@ define i32 @nsis_BZ2_bzDecompress(ptr %pos.i, i1 %cmp661.not3117.i, i1 %exitcond
 ; CHECK-NEXT:    // in Loop: Header=BB0_2 Depth=1
 ; CHECK-NEXT:    mov x9, xzr
 ; CHECK-NEXT:    ldrb w9, [x9]
-; CHECK-NEXT:    add x9, x0, x9
-; CHECK-NEXT:    strb wzr, [x9]
+; CHECK-NEXT:    strb wzr, [x0, x9]
 ; CHECK-NEXT:    b .LBB0_1
 ; CHECK-NEXT:  .LBB0_4: // %for.end677.i
 ; CHECK-NEXT:    mov w0, wzr

llvm/test/CodeGen/AArch64/sink-and-fold.ll

@@ -1,5 +1,5 @@
 ; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
-; RUN: llc -aarch64-enable-sink-fold=true < %s | FileCheck %s
+; RUN: llc < %s | FileCheck %s
 target triple = "aarch64-linux"
 
 declare i32 @use(...)