Reduce allocs by making SmartConstructors stateful

Summary:
Major refactoring of the parser in hope of squeezing
noticeable gains by not passing around SmartConstructors state.

Basically, replace the following:

  make_XYZ(state: State, ...) -> (State, R)

with

  make_XYZ(&mut self, ...) -> R

and make each of the 5 implementors of SmartConstructors stateful
by turning the old method `initial_state(...)` into constructor `new`.

Unfortunately, this means more boilerplate in the **user code**
(i.e., implementors of SmartConstructors):
- implementing Clone for each implementor of StateType
- implementing Clone for each implementor of SmartConstructors

this *cannot* be auto-generated via `#[derive(Clone)` because of
the [`PhantomData`](rust-lang/rust#29005 (comment)) that is needed to narrow down trait impl of `StateType`.

Reviewed By: shiqicao

Differential Revision: D16374645

fbshipit-source-id: 37c248e70d93dd505e5478a57b646ad469907d7c

hphp/hack/src/facts/facts_parser.rs

@@ -14,7 +14,7 @@ use parser::source_text::SourceText;
 use crate::facts::*;
 use crate::facts_smart_constructors::*;
 
-pub type FactsParser<'a> = Parser<'a, WithKind<FactsSmartConstructors>, HasScriptContent<'a>>;
+pub type FactsParser<'a> = Parser<'a, WithKind<FactsSmartConstructors<'a>>, HasScriptContent<'a>>;
 
 pub struct ExtractAsJsonOpts {
     pub php5_compat_mode: bool,