Invert default feature for testing (#1200)

## Summary

We have some flags in Puffin that enable us to opt-in to certain tests.
To date, they've been opt-in, so we've run our tests with
`--all-features`. This PR makes them opt-out, and we now run tests with
default features.

The main motivation here is that I want to get tests working for macOS
on CI, but for unknown reasons, macOS can't compile the PyO3 features at
the same time as everything else due to strange linker issues. By
avoiding `--all-features` for tests, we thus avoid unnecessarily
including features that we don't actually use in Puffin.

I verified that the exact same number of tests (439) are run before and
after this change. For users, the primary difference is that you now
need to specify `--no-default-features --features pypi --features
python` to avoid (e.g.) including the Git tests.

.github/workflows/ci.yml

@@ -70,7 +70,7 @@ jobs:
       - name: "Tests"
         run: |
           source .env
-          cargo nextest run --all --all-features --status-level skip --failure-output immediate-final --no-fail-fast -j 12
+          cargo nextest run --all --status-level skip --failure-output immediate-final --no-fail-fast -j 12
 
   # TODO(konstin): Merge with the cargo-test job once the tests pass
   windows:

crates/puffin-resolver/Cargo.toml

@@ -67,5 +67,6 @@ once_cell = { version = "1.19.0" }
 insta = { version = "1.34.0" }
 
 [features]
+default = ["pypi"]
 # Introduces a dependency on PyPI.
 pypi = []

crates/puffin/Cargo.toml

@@ -89,7 +89,7 @@ regex = { version = "1.10.3" }
 reqwest = { version = "0.11.23", features = ["blocking", "rustls"], default-features = false }
 
 [features]
-default = ["flate2/zlib-ng"]
+default = ["flate2/zlib-ng", "python", "pypi", "git", "maturin"]
 # Introduces a dependency on a local Python installation.
 python = []
 # Introduces a dependency on PyPI.