Interpreter: Refactor interface and lifetime management

Interpreter is now just a namespace with Run and Disassemble. This hides
all of the implementation details. In addition, the interpreter only used
the Program because of a few details in FunctionDeclarations - scrape that
when constructing a ByteCodeFunction, and we don't need to keep the entire
Program alive, just the ByteCode. Adjust tests to ensure that this works.

Change-Id: I61efe4fe986476afedbd295d3d55b2a326fea4e3
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/219521
Reviewed-by: Ethan Nicholas <ethannicholas@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
8 files changed