[RegisterConfiguration] Streamline access to arch defaults, simplify Registers.

src/arm64/assembler-arm64.cc

Index: src/arm64/assembler-arm64.cc
diff --git a/src/arm64/assembler-arm64.cc b/src/arm64/assembler-arm64.cc
index 7aea5bb135662bec839190ef6e5b0994503f660c..bd7dffc958d225ba4b10c162d2a81ee970a2249b 100644
--- a/src/arm64/assembler-arm64.cc
+++ b/src/arm64/assembler-arm64.cc
@@ -207,8 +207,7 @@ void RelocInfo::unchecked_update_wasm_memory_size(uint32_t size,
 Register GetAllocatableRegisterThatIsNotOneOf(Register reg1, Register reg2,
                                               Register reg3, Register reg4) {
   CPURegList regs(reg1, reg2, reg3, reg4);
-  const RegisterConfiguration* config =
-      RegisterConfiguration::ArchDefault(RegisterConfiguration::CRANKSHAFT);
+  const RegisterConfiguration* config = RegisterConfiguration::Crankshaft();
   for (int i = 0; i < config->num_allocatable_double_registers(); ++i) {
     int code = config->GetAllocatableDoubleCode(i);
     Register candidate = Register::from_code(code);