This loosens the connection to the AST interpreter and will allow us to
generate SourceRanges for the Bytecode interpreter in the future as well
Moves UnrealizedSourceRanges from TracebackFrame to the JS namespace for
this
Now ExecutionContext has vector of values that will represent values
of local variables.
This vector is initialized in ECMAScriptFunctionObject::internal_call()
or ECMAScriptFunctionObject::internal_const() using number of local
variables provided to ECMAScriptFunctionObject by the parser.
