Add diagnostic::on_unimplemented attribute on rust >=1.78

[wcampbell0x2a]

• Add the following diagnostics to hopefully lead people in the right direction when seeing trait problems related to ctxs and derives

error[E0277]: the trait bound `FieldF: deku::DekuReader<'_, _>` is not satisfied
  --> examples/example.rs:37:14
   |
37 |     field_f: FieldF,
   |              ^^^^^^ the trait `deku::DekuReader<'_, _>` is not implemented for `FieldF`
   |
   = note: implement by adding #[derive(DekuRead)] to `FieldF`
   = note: make sure the `ctx` sent into the function matches `FieldF`'s `ctx`
   = help: the following other types implement trait `deku::DekuReader<'a, Ctx>`:
             <() as deku::DekuReader<'_, Ctx>>
             <(A, B) as deku::DekuReader<'a, Ctx>>
             <(A, B, C) as deku::DekuReader<'a, Ctx>>
             <(A, B, C, D) as deku::DekuReader<'a, Ctx>>
             <(A, B, C, D, E) as deku::DekuReader<'a, Ctx>>
             <(A, B, C, D, E, F) as deku::DekuReader<'a, Ctx>>
             <(A, B, C, D, E, F, G) as deku::DekuReader<'a, Ctx>>
             <(A, B, C, D, E, F, G, H) as deku::DekuReader<'a, Ctx>>
           and 152 others

• Rust Release: https://blog.rust-lang.org/2024/05/02/Rust-1.78.0.html
• Rust MR: https://github.com/rust-lang/rust/pull/119888/

[github-actions[bot]]

Benchmark for 140a86b

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| Test | Base | PR | % | |------|--------------|------------------|---| | deku_read_bits | 1286.8±26.22ns | 1287.4±19.33ns | +0.05% | | deku_read_byte | 5.4±0.08ns | 5.4±0.12ns | 0.00% | | deku_read_enum | 2.6±0.07ns | 2.6±0.05ns | 0.00% | | deku_read_vec | 34.6±0.48ns | 34.5±0.48ns | -0.29% | | deku_write_bits | 160.9±1.77ns | 161.5±3.14ns | +0.37% | | deku_write_byte | 22.6±0.37ns | 22.7±0.33ns | +0.44% | | deku_write_enum | **21.4±0.30ns** | 21.8±0.37ns | **+1.87%** | | deku_write_vec | 439.0±6.14ns | **431.8±5.93ns** | **-1.64%** |