`find_path` blows up exponentially

In the project that can't be shared publicly rust-analyzer started hanging up all worker threads within find_path_module / calculate_best_path. I assume that it is not actually hanging (as the recursion does look like having appropriate exit conditions everywhere) but instead running into a search tree so wide that with a max depth of 15 (https://github.com/rust-lang/rust-analyzer/blob/cdb4f9631c88be66fc0ea84700f334600ace4a67/crates/hir-def/src/find_path.rs#L48) we just run into too much work to do depending on the project setup. Lowering that to 5 seemed to somewhat fix the issue in the project somewhat confirming my assumption

Start with crates/hir-def/src/find_path.rs, especially the max-depth setting near line 48 and the find_path_module/calculate_best_path entry points. Investigate the reported exponential search behavior and compare the effect of the depth limit; the private project cannot be used as a public reproduction, so completion requires a validated fix or regression coverage for excessive work.