Upgrade to hashbrown 0.14 and indexmap 2

[cuviper]

This doesn't need any code changes, but it does increase the MSRV.

• The base "read" MSRV is now 1.60, because hashbrown's use of the newer dependency syntax makes it invisible to older Cargo, which makes it un-resolvable even when hashbrown isn't feature-enabled.
  • I also took this opportunity to use the dep: syntax here, so hashbrown and indexmap don't show up as explicit features of object anymore. Maybe other optional dependencies could use this too.
• The "write" MSRV is now 1.64 to match the actual required versions of these new hashbrown and indexmap.

[cuviper]

which makes it un-resolvable even when hashbrown isn't feature-enabled.

Actually, I think this is only because the lockfile reflects all possible features. If you test from a separate workspace, it can live without resolving hashbrown, like serde_json did here:
serde-rs/json@d4c98d0

[philipc]

Split MSRV is fine, but I'm not sure about bumping to 1.60 yet.

Does testing from a separate workspace only help for tests that are in a separate crate?

[cuviper]

It does work if I use a new crate with a path dependency, use only --features read,std, then cargo +1.52.0 test -p object. Let me see if I can put that to use in CI...

[cuviper]

Seems to work locally, but we'll see when you push that CI button. :)

[philipc]

Ah, I didn't know you could run tests for another package like that. Unfortunately it only works when there are no dev dependencies, so we can't do this for the tests in crates/examples as well. I think this is too much of a hack and we should just bump to 1.60 instead.

[cuviper]

Okay, I've reset this back to how I had it before.