Use cargo-all-features to test all combinations of features

[frewsxcv]

WIP

[michaelkirk]

I really like cargo-test-all-features...

e.g. it caught this bug georust/wkt#59 (comment)

It's currently pretty slow for the proj crate, but maybe that's OK. It'd be a real milestone if enough development was happening that CI became the bottleneck. 🙃

[frewsxcv]

@michaelkirk Well this PR is basically ready to go. I just wasn't sure about removing the _PROJ_SYS_TEST_EXPECT_BUILD_FROM_SRC test 🤷🏻

[michaelkirk]

I just wasn't sure about removing the _PROJ_SYS_TEST_EXPECT_BUILD_FROM_SRC test 🤷🏻

Oh right I forgot about that... I do like being able to test that we're building / not building from source.

I don't see how to reconcile that with cargo-test-all-features...

We could add another mostly-redundant cargo test-all-features job, just to make sure the compiler doesn't explode under any feature combinations, but I'm not sure if it's worth it.

sorry for the 🧇 🧇 🧇 🧇 🧇 🧇 🧇 🧇