pdl: Relax parsing to allow trailing data

It turns out that UWB has code which expects to pass more data than
necessary to the parsing code. We will allow this for now and then
work on communicating the trailing data back to the user later.

Tag: #feature
Bug: 228306436
Test: atest pdl_tests pdl_rust_generator_tests_{le,be}
Change-Id: I87c1f88dba782bb25e437a388617fcfcf2fd9c6d