Even more clippy lints could be turned on

          > I put them in the `units` manifest.

Sounds good! Let's dig a bit further when we do the second crate to see if we can de-dupe.

Some more lints I think we should add, maybe in a followup:

• cargo_common_metadata
• clear_with_drain
• clone_on_ref_ptr (forces explicit Arc::clone when cloning Arcs, which IMO is good style)
• collection_is_never_read
• debug_assert_with_mut_call
• Maybe decimal_literal_representation ... this e.g. complains if you write 32768 instead of 0x8000.
• deref_by_slicing
• equatable_if_let (IMO this is good style, but you may disagree)
• empty_structs_with_brackets
• Maybe else_if_without_else ... this isa MISRA C guideline and also I dated a girl a long time ago who told me to do this
• fallible_impl_from (should lint panics in From, a pet peeve of Kix's)
• float_arithmetic lints any use of float arithmetic ... maybe have this as warn and whitelist specific modules?
• fn_to_numeric_cast_any
• imprecise_flops (improve FP accuracy, though maybe at expense of performance)
• large_stack_frames (goes with large_stack_array)
• manual_clamp (goes with other manual_* lints we already have)
• non_ascii_idents (this is actually a rustc lint now... unsure if it's on by default)
• Maybe pattern_type_mismatch (this is a personal pet peeve of mine, YMMV)
• Maybe multiple_inherent_impl and module_name_repetitions .. unsure
• needless_collect
• string_add (goes with string_add_assign)
• std_instead_of_core, std_instead_of_alloc, alloc_instead_of_core which lints imports from too-strong a place
• significant_drop_tightening (suggests moving mutex drops up) and maybe significant_drop_in_scrutinee (not really sure what this does)i

There is also missing_enforced_import_renames which requires explicit configuration.

There is also arithmetic_side_effects which lints all potentially-panicking arithmetic. Can be configured. May be worth exploring or maybe just way too noisy.

Originally posted by @apoelstra in https://github.com/rust-bitcoin/rust-bitcoin/issues/3704#issuecomment-2541736964

Start with the units manifest and the repository's existing Clippy lint configuration. Review the listed lints and their configuration needs, then determine which are appropriate for the second crate; done means the selected lints are enabled without unacceptable warnings or noise.