pdl: Align Rust canonical tests with source

I’ve been copying bits and pieces from the source files into the Rust
file and the definition has been accidentally reordered. They’re now
brought back in line with the source files.

Test: atest pdl_tests pdl_rust_generator_tests_{le,be}
(cherry picked from https://android-review.googlesource.com/q/commit:81d367cc2b7632e632832f30244516f1d15ea6cb)
Merged-In: I41c26557b90e5f17e3dc7304def6f2dbb1e09ec3
Change-Id: I41c26557b90e5f17e3dc7304def6f2dbb1e09ec3