Camera2: Cache method list in MethodNameInvoker.

Retrieving list of methods in every invoke() call is very expensive.
Caching the list inside the constructor prevents several unnecessary
calls to Class.getMethods().

Test: Run camera2 CTS
Bug: 62490715

Change-Id: Ib2a93af0f364b055df2eab9bd7870730428429ad
1 file changed