Simplify CI testing matrix

[lnicola]

• I agree to follow the project's code of conduct.
• I added an entry to CHANGES.md if knowledge of this change could be valuable to users.

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Closes #672

[lnicola]

This reduces the CI time from 26 to 6.5 minutes.

[rmanoka]

Should we also disable testing the proj-network feature or leave it as-is until it causes some test breaks?

[lnicola]

I wanted to, but was worried we wouldn't test new features. But yeah, let's try it.

[lnicola]

Updated.

[rmanoka]

Lgtm! Let's see if anyone with more knowledge of the proj integration has some comments. Ping @michaelkirk @urschrei .

[urschrei]

I'm trying to think of ways in which not testing the network functionality could cause an issue for geo, but so far I'm coming up blank: all the functionality enabled by the feature is in the proj crate, releases of which are gated on passing tests (which include testing network functionality). The feature builds our bundled version of proj, adding a build dependency on libtiff, as well as depending on 'reqwest'.

[michaelkirk]

For posterity, can you add a comment as to why we're not doing --all-features here

[lnicola]

Sure, added a comment.

[urschrei]

Looks like we're down to ~7 minutes now, with the bench job taking the longest.

[michaelkirk]

bors r+

Let's do it!

[bors]

Build succeeded:

• ci result

[michaelkirk]

/cc @frewsxcv re: #671 (comment)

I just wanted to make sure that you saw this PR was merged.

In hindsight, I should have tagged you earlier, since I know you are especially interested in our testing strategy.