Android test updates

[mhsmith]

• Use Android environment markers when installing the test environment – see pybind11#5809.

• Pass the build-verbosity setting through to the test runner.

• I thought I'd need to add support for test-groups, but it turns out this already works (#2574).

[mhsmith]

@freakboy3742: The iOS tests have failed several times in the last 2 days, but only on macos-14. I don't see any obvious explanation in the logs.

[freakboy3742]

@freakboy3742: The iOS tests have failed several times in the last 2 days, but only on macos-14. I don't see any obvious explanation in the logs.

As far as I can make out, it's a timeout launching the simulator. Launch times on macOS-14 have always significantly slower than macOS-15 - it's not clear why, but possibly due to a change/improvement in Xcode 16.

The prevalence of that mode of failure will be exacerbated by the way we're launching the simulator (i.e., the 2-thread parallelised build approach). My hope is that when I push out new support packages that use the single-threaded approach, we can move back to macOS-15, which should make this sort of failure much less common.