Revert "Update for Rust v1.62.0"

This partially reverts commit
f0b6afce.

Reason for revert: The `format_push_string` lint suggests changing
infallable code to a new style where we throw away the error we "know"
cannot occur. This is not an improvement and the lint was now moved to
the "restriction" category:
https://github.com/rust-lang/rust-clippy/commit/10e85efc

Test: atest pdl_inline_tests pdl_tests
Change-Id: Ic256ce31ba46ccf9d3b7da46f6c67ce1f497fc79