cli: Load `libjulia-*` by filepath, not basename (#62470)
This library deduplication in the CLI loader can lead to us mis-wiring
our trampolines in Julia-in-Julia scenarios.
We mostly did not notice this because many runtime symbol references use
the "internal" version of symbols rather than the trampolines in
`libjulia`, but it obviously wreaks havoc in embedding scenarios that
load multiple copies of Julia side-by-side.
Along with #62465, this should be enough to restore this functionality
to working order.
