pdl: Format generated code using prettyplease

This removes the need for using rustfmt when invoking pdl.

Tag: #refactor
Bug: 274187738
Test: atest pdl_tests pdl_rust_generator_tests_{le,be} pdl_generated_files_compile
Change-Id: Ia49e6b2aec53b9c23d62532b7fcdfbc59ca723ca