Out of memory when trying to analyze big auto-generated files

Follow-up of #13788.

Rust analyzer no longer panics when trying to parse big files. However, now my system OOMs (16 GB of RAM) while trying to analyze the generated files.

EDIT:
This only happens after triggering a cargo check on save. I tested cargo check alone and it only consumes 3+GB of RAM, so the problem seems to be R-A.

To reproduce

git clone https://github.com/jedel1043/ra-bug.git && cd ra-bug

Depending on the base memory consumption, the used memory should increase by 8+ GB after opening the project and triggering a cargo check. For some high-end systems this should not be a problem, but the standalone repo bumps the used memory to approx. 15.8 GB on my system, and trying to use the crate in a mid-sized workspace project directly OOMs.

rust-analyzer version: 0.4.1326-standalone

rustc version: rustc 1.66.0 (69f9c33d7 2022-12-12)

cc @Manishearth

Clone the linked ra-bug repository and reproduce the report by opening the project and triggering cargo check on save; compare this with running cargo check alone. Use the reported rust-analyzer 0.4.1326-standalone and rustc 1.66.0 versions as context. Done means analyzing the generated files no longer causes the reported multi-gigabyte memory increase or out-of-memory failure.