This changes the reqwest client used in tests to be sandbox-friendly,
and skips a bunch of other tests that don't work inside the
sandbox/without network.
`test_shell_command_approval_triggers_elicitation()` is one of a number
of integration tests that we have observed to be flaky on GitHub CI, so
this PR tries to reduce the flakiness _and_ to provide us with more
information when it flakes. Specifically:
- Changed the command that we use to trigger the elicitation from `git
init` to `python3 -c 'import pathlib; pathlib.Path(r"{}").touch()'`
because running `git` seems more likely to invite variance.
- Increased the timeout to wait for the task response from 10s to 20s.
- Added more logging.
this dramatically improves time to run `cargo test -p codex-core` (~25x
speedup).
before:
```
cargo test -p codex-core 35.96s user 68.63s system 19% cpu 8:49.80 total
```
after:
```
cargo test -p codex-core 5.51s user 8.16s system 63% cpu 21.407 total
```
both tests measured "hot", i.e. on a 2nd run with no filesystem changes,
to exclude compile times.
approach inspired by [Delete Cargo Integration
Tests](https://matklad.github.io/2021/02/27/delete-cargo-integration-tests.html),
we move all test cases in tests/ into a single suite in order to have a
single binary, as there is significant overhead for each test binary
executed, and because test execution is only parallelized with a single
binary.
