feat: More callable info
With this PR we retain more info about callables other than functions, allowing for closure parameter type inlay hints to be linkable as well as better signature help around closures and `Fn*` implementors.
In the stabilization attempt of `#[unix_sigpipe = "sig_dfl"]`, a concern
was raised related to using a language attribute for the feature: Long
term, we want `fn lang_start()` to be definable by any crate, not just
libstd. Having a special language attribute in that case becomes
awkward.
So as a first step towards towards the next stabilization attempt, this
PR changes the `#[unix_sigpipe = "..."]` attribute to a compiler flag
`-Zon-broken-pipe=...` to remove that concern, since now the language
is not "contaminated" by this feature.
Another point was also raised, namely that the ui should not leak
**how** it does things, but rather what the **end effect** is. The new
flag uses the proposed naming. This is of course something that can be
iterated on further before stabilization.
Have Derive Attribute share a token tree with it's proc macros.
The goal of this PR is to stop creating a token tree for each derive proc macro.
This is done by giving the derive proc macros an id to its parent derive element.
From running the analysis stat on the rust analyzer project I did see a small memory decrease.
```
Inference: 42.80s, 362ginstr, 591mb
MIR lowering: 8.67s, 67ginstr, 291mb
Mir failed bodies: 18 (0%)
Data layouts: 85.81ms, 609minstr, 8mb
Failed data layouts: 135 (6%)
Const evaluation: 440.57ms, 5235minstr, 13mb
Failed const evals: 1 (0%)
Total: 64.16s, 552ginstr, 1731mb
```
After Change
```
Inference: 40.32s, 340ginstr, 593mb
MIR lowering: 7.95s, 62ginstr, 292mb
Mir failed bodies: 18 (0%)
Data layouts: 87.97ms, 591minstr, 8mb
Failed data layouts: 135 (6%)
Const evaluation: 433.38ms, 5226minstr, 14mb
Failed const evals: 1 (0%)
Total: 60.49s, 523ginstr, 1680mb
```
Currently this breaks the expansion for the actual derive attribute.
## TODO
- [x] Pick a better name for the function `smart_macro_arg`
