pdl: Refactor analyzer

Modify the analyzer to process the input AST to:
  - annotate fields and types with the size in bits
  - inline group fields

Test: cargo test analyzer::test
(cherry picked from https://android-review.googlesource.com/q/commit:81ff283aeae6f7f8fa0cfa8b4393e96dc5232858)
Merged-In: I0e9165c32aa0220faa2ca6bd29dec7d4096ebc51
Change-Id: I0e9165c32aa0220faa2ca6bd29dec7d4096ebc51