Resolve open TODOs in code

[mpguerra]

I think we might be able to do this one now that div_ceil has been stabilised in the latest rust release (1.73.0)?

frost/frost-core/src/scalar_mul.rs

Line 24 in b37bde0

// TODO: remove this function and use `div_ceil()` instead when `int_roundings`

[conradoplg]

We might want to wait a bit. If we do that now then everyone who uses our crates will need to use at least Rust 1.73.0 and that may be too strict. Maybe until the next Rust stable release?

[mpguerra]

Scheduling until after next Rust stable release on 2023.11.16

[mpguerra]

this blocks tagging the stable release

[mpguerra]

Let's wait until ECC crates are on 1.73.0 as their MSRV