Switch loom to dev-dependency

[Blizzara]

Hey, thanks for making and maintaing this crate! I was looking at the dependencies it introduces downstream in my project, and among them is loom:

[[package]]
name = "moka"
version = "0.12.10"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "a9321642ca94a4282428e6ea4af8cc2ca4eac48ac7a6a4ea8f33f76d0ce70926"
dependencies = [
 "async-lock",
 "crossbeam-channel",
 "crossbeam-epoch",
 "crossbeam-utils",
 "event-listener",
 "futures-util",
 "loom",
 "parking_lot",
 "portable-atomic",
 "rustc_version",
 "smallvec",
 "tagptr",
 "thiserror 1.0.69",
 "uuid",
]

However it seems that loom is only used for testing, could it be made a dev-dependency instead? Currently it's a normal dep:

moka/Cargo.toml

Line 88 in e970c84

[target.'cfg(moka_loom)'.dependencies]

but the lines below use dev-dependency.

I may be missing something here in case that isn't possible, but if it is it could be a nice improvement :)