add an LRU cache to precompile files

[KristofferC]

instead of always clobbering the one precompile file per package for multiple environments, introduce a LRU cache (maximum of, currently, 10 files).

Fixes #27418

[KristofferC]

cc @tkf who have been thinking about these stuff as well

[KristofferC]

Thinking about this a little more the implementation in this PR is non ideal because iteratively working on a project for a while will quickly clobber the whole cache of precompilation files.

We need to get the path of the current active project in there. Will amend this PR.

[tkf]

We need to get the path of the current active project in there.

I think the tricky part is supporting switching projects. If you interleave Pkg.activates with imports, the "effective manifest" of the current process would be hard to re-construct in precompilation subprocesses.

I think an easier solution would be to use Base.HOME_PROJECT[] as a salt in package_slug. That is to say, we only guarantee that julia --project A and julia --project B have separate precompilation file set. Starting a session with julia and then pkg> activate A or pkg> activate B will still clobber the precompilation files.

[tkf]

Re early my comment #32651 (comment)
I'm now convinced that my concern is invalid. This PR seems to be a very clever solution!

[andreasnoack]

Let's merge this by the end of the day unless somebody speaks up. This is a great improvement over the current situation so it would be good to have included in 1.3 even if we want to adjust the details later.

[bjarthur]

less clobbering of precompilation files when changing environments is the #1 reason i'd upgrade to 1.3. unless i missed it, this PR is not mentioned in HISTORY.md. worth adding i think.