[Interpreter] Replace BytecodeRegisterAllocator with a simple bump pointer.

test/cctest/interpreter/bytecode_expectations/LetVariable.golden

Index: test/cctest/interpreter/bytecode_expectations/LetVariable.golden
diff --git a/test/cctest/interpreter/bytecode_expectations/LetVariable.golden b/test/cctest/interpreter/bytecode_expectations/LetVariable.golden
index b2f4d3840244376ee038134d8a8c14e7fb8def8c..5c6897dc080e1d11e3c98fd0da570922ee33dacf 100644
--- a/test/cctest/interpreter/bytecode_expectations/LetVariable.golden
+++ b/test/cctest/interpreter/bytecode_expectations/LetVariable.golden
@@ -58,7 +58,7 @@ snippet: "
 "
 frame size: 3
 parameter count: 1
-bytecode array length: 26
+bytecode array length: 29
 bytecodes: [
                 B(LdaTheHole),
                 B(Star), R(0),
@@ -71,6 +71,7 @@ bytecodes: [
                 B(Star), R(2),
   /*   45 E> */ B(CallRuntime), U16(Runtime::kThrowReferenceError), R(2), U8(1),
                 B(Mov), R(1), R(0),
+                B(Mov), R(1), R(0),
                 B(LdaUndefined),
   /*   52 S> */ B(Return),
 ]