[Interpreter] Replace BytecodeRegisterAllocator with a simple bump pointer.

test/cctest/interpreter/bytecode_expectations/WithStatement.golden

 #
 # Autogenerated by generate-bytecode-expectations.
 #
 
 ---
 execute: yes
 wrap: yes
 
 ---
 snippet: "
   with ({x:42}) { return x; }
 "
-frame size: 3
+frame size: 2
 parameter count: 1
 bytecode array length: 22
 bytecodes: [
   /*   30 E> */ B(StackCheck),
   /*   34 S> */ B(CreateObjectLiteral), U8(0), U8(0), U8(1), R(1),
                 B(Ldar), R(1),
-                B(ToObject), R(2),
+                B(ToObject), R(1),
                 B(Ldar), R(closure),
-                B(CreateWithContext), R(2), U8(1),
+                B(CreateWithContext), R(1), U8(1),
                 B(PushContext), R(0),
   /*   50 S> */ B(LdaLookupSlot), U8(2),
                 B(PopContext), R(0),
   /*   62 S> */ B(Return),
 ]
 constant pool: [
   FIXED_ARRAY_TYPE,
   FIXED_ARRAY_TYPE,
   ONE_BYTE_INTERNALIZED_STRING_TYPE ["x"],
 ]
 handlers: [
 ]