pdl: Generate canonical serialization tests

This will exercise the builder API in the generated code.

Test: atest pdl_rust_generator_tests_{le,be}
(cherry picked from https://android-review.googlesource.com/q/commit:836b43427f40ed5fd521b50bde5733caa15132b0)
Merged-In: I3dc4c2d7a76d03186acd0a6a27ce3d901910b906
Change-Id: I3dc4c2d7a76d03186acd0a6a27ce3d901910b906