use cortex-m-types crate for the InterruptNumber trait

[robamu]

this is a part of the effort to make updating cortex-m easier. PACs can now depend on cortex-m-types instead of cortex-m

[burrbull]

Makes sense. Could you add discussion link in first message, please?

[robamu]

which discussion link? this PR?

[robamu]

Also had to bump the MSRV.

[burrbull]

which discussion link?

Where cortex-m-types was introduced.

[robamu]

I can not find it. maybe because cortex-m was not always a mono-repo?

[burrbull]

/ci diff

[adamgreig]

Might be worth a note that PACs generated using cortex-m-types won't export an InterruptNumber that works with current cortex-m's NVIC (https://docs.rs/cortex-m/latest/cortex_m/peripheral/struct.NVIC.html). I think we can publish a new cortex-m 0.7.x that has a blanket impl of its InterruptNumber trait for the one from cortex-m-types that would maintain compatibility, but need to check that actually works.