feat: Add "make tuple" tactic to term search

[kilpkonn]

Follow up to #16092

Now term search also supports tuples.

let a: i32 = 1;
let b: f64 = 0.0;
let c: (i32, (f64, i32)) = todo!(); // Finds (a, (b, a))

In addition to new tactic that handles tuples I changed how the generics are handled.
Previously it tried all possible options from types we had in scope but now it only tries useful ones that help us directly towards the goal or at least towards calling some other function.
This changes O(2^n) to O(n^2) where n is amount of rounds which in practice allows using types that take generics for multiple rounds (previously limited to 1). Average case that also used to be exponential is now roughly linear.
This means that deeply nested generics also work.

// Finds all valid combos, including `Some(Some(Some(...)))`
let a: Option<Option<Option<bool>>> = todo!();

Note that although the complexity is smaller allowing more types with generics the search overall slows down considerably. I hope it's fine tho as the autocomplete is disabled by default and for code actions it's not super slow. Might have to tweak the depth hyper parameter tho

This resulted in a huge increase of results found (benchmarks on ripgrep crate):
Before

Tail Expr syntactic hits: 149/1692 (8%)
Tail Exprs found: 749/1692 (44%)
Term search avg time: 18ms

After

Tail Expr syntactic hits: 291/1692 (17%)
Tail Exprs found: 1253/1692 (74%)
Term search avg time: 139ms

Most changes are local to term search except some tuple related stuff on hir::Type.

[Veykril]

That does not sound good 😬

[kilpkonn]

Yeah 😛
It'happened once for FromStr::from_str in ripgrep crate. Got no idea how that case was special tho

[Veykril]

@bors r+

[bors]

📌 Commit a2bf15e has been approved by Veykril

It is now in the queue for this repository.

[bors]

⌛ Testing commit a2bf15e with merge 6b250a2...

[bors]

☀️ Test successful - checks-actions
Approved by: Veykril
Pushing 6b250a2 to master...