Fix OOM caused by term search
The issue came from multi Cartesian product for exprs with many (25+) arguments, each having multiple options.
The solution is two fold:
### Avoid blowing up in Cartesian product
**Before the logic was:**
1. Find expressions for each argument/param - there may be many
2. Take the Cartesian product (which blows up in some cases)
4. If there are more than 2 options throw them away by squashing them to `Many`
**Now the logic is:**
1. Find expressions for each argument/param and squash them to `Many` if there are more than 2 as otherwise we are guaranteed to also have more than 2 after taking the product which means squashing them anyway.
2. Take the Cartesian product on iterator
3. Start consuming it one by one
4. If there are more than 2 options throw them away by squashing them to `Many` (same as before)
This is also why I had to update some tests as the expressions get squashed to many more eagerly.
### Use fuel to avoid long search times and high memory usage
Now all the tactics use `should_continue: Fn() -> bool` to chech if they should keep iterating _(Similarly to chalk)_.
This reduces the search times by a magnitude, for example from ~139ms/hole to ~14ms/hole for `ripgrep` crate.
There are slightly less expressions found, but I think speed gain worth it for usability.
Also note that syntactic hits decreases more because of squashing so you simple need to run search multiple times to get full terms.
Also the worst case time (For example `nalgebra` crate cus it has tons of generics) has search times mostly under 200ms.
Benchmarks on `ripgrep` crate
Before:
```
Tail Expr syntactic hits: 291/1692 (17%)
Tail Exprs found: 1253/1692 (74%)
Term search avg time: 139ms
````
After:
```
Tail Expr syntactic hits: 239/1692 (14%)
Tail Exprs found: 1226/1692 (72%)
Term search avg time: 14ms
```
When viewing traces, it's slightly confusing when the span name doesn't
match the function name. Ensure the names are consistent.
(It might be worth moving most of these to use #[tracing::instrument]
so the name can never go stale. @davidbarsky suggested that is marginally
slower, so I've just done the simple change here.)
feat: Syntax highlighting improvements
Specifically
- Adds a new `constant` modifier, attached to keyword `const` (except for `*const ()` and `&raw const ()`), `const` items and `const` functions
- Adds (or rather reveals) `associated` modifier for associated items
- Fixes usage of the standard `static` modifier, now it acts like `associated` except being omitted for methods.
- Splits `SymbolKind::Function` into `Function` and `Method`. We already split other things like that (notable self param from params), so the split makes sense in general as a lot special cases around it anyways.
Abstract more over ItemTreeLoc-like structs
Allows reducing some code duplication by using functions generic over said structs. The diff isn't negative due to me adding some additional impls for completeness.
This commit also adds `tracing` to NotificationDispatcher/RequestDispatcher,
bumps `rust-analyzer-salsa` to 0.17.0-pre.6, `always-assert` to 0.2, and
removes the homegrown `hprof` implementation in favor of a vendored
tracing-span-tree.
