Move the following unit types to the new `units` crate:
- `locktime::absolute::{Height, Time}`
- `locktime::relative::{Height, Time}`
- `FeeRate`
- `Weight`
Also move the `parse` module as well as constants as required.
Do minimal changes to get things building:
- Feature gate on "alloc" as needed.
- Remove rustdocs that use `bitcoin` types.
- Re-export units types so this is a non-breaking change.
- Fix import paths.
Make the trait level attributes uniform across all released crates in
the repo. Excludes things that are obviously not needed, eg, bench stuff
if there is not bench code.
- Remove `uninhabited_references` - this is allow by default now.
- Remove `unconditional_recursion` and mark the single false positive we
have with an `allow`.
Note, this does not add `missing_docs` to the `io` crate. There is an
open PR at the moment to add that along with the required docs.
Previously the crate used negative reasoning to enable `std` which was
hard to understand, required the `prelude` module and wasn't really
needed because it's only needed when a crate wants to add `alloc`
feature-backwards compatibly and this crate always had the feature.
This cleans up usage to unconditionally use `#[no_std]` and then just
add `extern crate` on top as needed by activated features.
Using the crate without allocation was previously disabled making the
crate empty without the feature. This chage makes it more fine-grained:
it only disables string and float conversions which use allocator. We
could later provide float conversions by using a sufficiently-long
`ArrayString`.