New api

[Muscraft]

This PR moves annotate-snippets internals to better match rustc, better matches rustc's output, adds suggestions, and moves to a new API. The new API is subject to change as user feedback comes in on how it can be improved.

[epage]

We've discussed this offline and with the branch.

I expect we'll iterate further within the repo, rather than keep this massive change in the dark further

[zbraniecki]

this reads great! Thank you for driving the update.
I'm surprised how little the code changes and I like the Group semantics.

I checked the benchmarks between today's master:

❯ cargo criterion
    Finished `bench` profile [optimized + debuginfo] target(s) in 0.08s

running 0 tests

test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s

Timer precision: 41 ns
bench         fastest       │ slowest       │ median        │ mean          │ samples │ iters
├─ fold                     │               │               │               │         │
│  ├─ 0       3.915 µs      │ 41.49 µs      │ 4.041 µs      │ 4.507 µs      │ 100     │ 100
│  ├─ 1       3.874 µs      │ 4.79 µs       │ 3.999 µs      │ 4.046 µs      │ 100     │ 100
│  ├─ 10      3.999 µs      │ 5.749 µs      │ 4.124 µs      │ 4.16 µs       │ 100     │ 100
│  ├─ 100     5.165 µs      │ 6.833 µs      │ 5.249 µs      │ 5.296 µs      │ 100     │ 100
│  ├─ 1000    16.45 µs      │ 94.54 µs      │ 16.58 µs      │ 18.01 µs      │ 100     │ 100
│  ├─ 10000   129.6 µs      │ 182.2 µs      │ 133.7 µs      │ 137.8 µs      │ 100     │ 100
│  ╰─ 100000  1.289 ms      │ 1.829 ms      │ 1.413 ms      │ 1.443 ms      │ 100     │ 100
╰─ simple     28.79 µs      │ 45.54 µs      │ 29.08 µs      │ 29.66 µs      │ 100     │ 100

and your PR:

❯ cargo criterion
    Finished `bench` profile [optimized + debuginfo] target(s) in 0.08s

running 0 tests

test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s

Timer precision: 41 ns
bench         fastest       │ slowest       │ median        │ mean          │ samples │ iters
├─ fold                     │               │               │               │         │
│  ├─ 0       4.041 µs      │ 46.12 µs      │ 4.166 µs      │ 4.616 µs      │ 100     │ 100
│  ├─ 1       3.999 µs      │ 5.207 µs      │ 4.166 µs      │ 4.195 µs      │ 100     │ 100
│  ├─ 10      4.124 µs      │ 5.832 µs      │ 4.291 µs      │ 4.324 µs      │ 100     │ 100
│  ├─ 100     5.457 µs      │ 7.374 µs      │ 5.583 µs      │ 5.629 µs      │ 100     │ 100
│  ├─ 1000    17.41 µs      │ 19.37 µs      │ 17.58 µs      │ 17.62 µs      │ 100     │ 100
│  ├─ 10000   132.5 µs      │ 253.4 µs      │ 137.8 µs      │ 141.3 µs      │ 100     │ 100
│  ╰─ 100000  1.295 ms      │ 1.658 ms      │ 1.444 ms      │ 1.441 ms      │ 100     │ 100
╰─ simple     29.62 µs      │ 49.2 µs       │ 29.95 µs      │ 30.32 µs      │ 100     │ 100

Seems all good!