Make CI build & test use default and all feature sets

[echeran]

This is to allow both the build and test commands in cargo to run both with default features enabled and with --all-features.

I was not able to use --no-default-features:

$ cargo build --no-default-features
error: --no-default-features is not allowed in the root of a virtual workspace
note: while this was previously accepted, it didn't actually do anything
$ cargo test --no-default-features
error: --no-default-features is not allowed in the root of a virtual workspace
note: while this was previously accepted, it didn't actually do anything

A test run shows the locale component's serde unit tests running when all features (including the serde feature) are enabled, and they don't run in the default setting, as expected.

Is the lack of --no-default-features okay for this PR, or should I continue looking into cargo-all-features as @zbraniecki mentioned in order to address the scenario of testing with std disabled?

[filmil]

You could make a cargo manifest non-virtual, in which case I think cargo will allow you to do this.

[coveralls]

Pull Request Test Coverage Report for Build a25634d21fd1555074bc1a501a904e7a1a2b8fe3-PR-121

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 87.199%

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Totals
Change from base Build a0d0cfec033b6db6a500c927cca7bc7e5beff280:	0.0%
Covered Lines:	688
Relevant Lines:	789

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💛 - Coveralls

[zbraniecki]

I'm ok with this PR. We can add test-all-features later.

[sffc]

An improvement for now, and hopefully we can figure out how to get the no-feature build working as well.

[sffc]

Main issue: #63