Auto merge of #9541 - Alexendoo:declare-proc-macro, r=flip1995

Generate lint categories and explanations with `declare_clippy_lint`

This means contributors will no longer have to run `cargo dev update_lints` after changing a lints documentation or its category, which may also mean fewer merge conflicts in general

It works by swapping `declare_clippy_lint` out for a `proc_macro` of the same name. The proc macro emits a `LintInfo` alongside the generated `Lint` which are gathered into `declared_lint::LINTS`. The categories/explanations are then read from `declared_lint::LINTS` at runtime

The removal of `src/docs` is split into a separate commit to be more easily ignored

It is slightly slower though, adding a bit under a second to build time. Less noticeable in full builds or with a slower linker (benchmark uses mold)

```bash
hyperfine --warmup 2 \
    --parameter-list commit "declare-proc-macro,master" \
    --command-name "{commit}" \
    --setup "git checkout {commit}" \
    --prepare "touch clippy_lints/src/lib.rs" \
    "cargo build"
```
```
Benchmark 1: declare-proc-macro
  Time (mean ± σ):     10.731 s ±  0.154 s    [User: 7.739 s, System: 1.791 s]
  Range (min … max):   10.598 s … 11.125 s    10 runs

Benchmark 2: master
  Time (mean ± σ):      9.422 s ±  0.094 s    [User: 7.183 s, System: 1.732 s]
  Range (min … max):    9.287 s …  9.624 s    10 runs

Summary
  'master' ran
    1.14 ± 0.02 times faster than 'declare-proc-macro'
```

r? `@flip1995`
cc `@llogiq` for `--explain`

changelog: none

1 files changed, 0 insertions, 41 deletions

diff --git a/src/docs/large_enum_variant.txt b/src/docs/large_enum_variant.txt
deleted file mode 100644
index 1f95430790d..00000000000
--- a/src/docs/large_enum_variant.txt
+++ /dev/null
@@ -1,41 +0,0 @@
-### What it does
-Checks for large size differences between variants on
-`enum`s.
-
-### Why is this bad?
-Enum size is bounded by the largest variant. Having one
-large variant can penalize the memory layout of that enum.
-
-### Known problems
-This lint obviously cannot take the distribution of
-variants in your running program into account. It is possible that the
-smaller variants make up less than 1% of all instances, in which case
-the overhead is negligible and the boxing is counter-productive. Always
-measure the change this lint suggests.
-
-For types that implement `Copy`, the suggestion to `Box` a variant's
-data would require removing the trait impl. The types can of course
-still be `Clone`, but that is worse ergonomically. Depending on the
-use case it may be possible to store the large data in an auxiliary
-structure (e.g. Arena or ECS).
-
-The lint will ignore the impact of generic types to the type layout by
-assuming every type parameter is zero-sized. Depending on your use case,
-this may lead to a false positive.
-
-### Example
-```
-enum Test {
-    A(i32),
-    B([i32; 8000]),
-}
-```
-
-Use instead:
-```
-// Possibly better
-enum Test2 {
-    A(i32),
-    B(Box<[i32; 8000]>),
-}
-```
\ No newline at end of file