Remove automatic name mangling from DSL.

This feature is always disabled when DSLParser is used. Name mangling
was only useful when compiling hand-authored DSL code that explicitly
declared two variables with the same name in separate scopes. In
practice, as long as we aren't declaring complete programs in DSL form,
we don't need this.

Change-Id: Icad921eb86365b3b114ff1872b1c40c41470a4b4
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/541637
Reviewed-by: Brian Osman <brianosman@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
12 files changed