Use cargo-all-features for all feature sets (incl. no features)

[echeran]

Summary:

• Using cargo-all-features appears to build and test against all subsets of features (including no features) as expected
• The build step (cargo build-all-features) ends early with an error
• The test step (cargo test-all-features), when run locally, shows some of the combinations in its output
• The reported errors may not be the exhaustive list, since the process exits early on error
• example workflow run

Fixes #63

Selected lines from build run:

    Building crate=icu-data-provider features=[]

error[E0432]: unresolved import `std::error`
  --> components/data-provider/src/lib.rs:16:10
   |
16 | use std::error::Error;
   |          ^^^^^ help: a similar path exists: `downcast_rs::std::error`

error: aborting due to previous error

For more information about this error, try `rustc --explain E0432`.
error: could not compile `icu-data-provider`.

Selected lines from test run:

     Testing crate=icu4x features=[]

     Testing crate=icu-data-provider-json features=[]

     Testing crate=icu-data-provider-json features=[std]

     Testing crate=icu features=[]

     Testing crate=icu-data-provider features=[]

error[E0432]: unresolved import `std::error`
  --> components/data-provider/src/lib.rs:16:10
   |
16 | use std::error::Error;
   |          ^^^^^ help: a similar path exists: `downcast_rs::std::error`

error: aborting due to previous error

For more information about this error, try `rustc --explain E0432`.
error: could not compile `icu-data-provider`.

[coveralls]

Pull Request Test Coverage Report for Build 86273e465d7b795d63847d8239ce4fe159b3b2c7-PR-169

• 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 e555f25bad0ae5af43dda697328c787944a4252e:	0.0%
Covered Lines:	688
Relevant Lines:	789

---

💛 - Coveralls

[sffc]

I'm confused. The diff in this PR shows you adding the Clippy check that you added in #161.

[echeran]

Hmm, I got the source branch misconfigured -- I should have used echeran:ci-all-features. This PR mistakenly uses echeran:master as the source branch b/c it's the only easy way to do iterative testing of Github Actions on a personal fork without disrupting an open PR. I'll re-create this PR but with the correct branch configured.

[echeran]

Closing & moving this PR over to #172 .