rust/sedona-raster-zarr: Find route to unignore network tests

There are a few `#[ignore]`d tests that use network access in the sedona-raster-zarr crate. We should either unignore them, move the network accesses to something that in theory is stable (e.g., sedona-testing), or run them less frequently to reduce the stress we put on the external servers (e.g., only on commit to `main` via environment variable, or weekly together with other slow tests or benchmarks).

_Originally posted by @paleolimbot in https://github.com/apache/sedona-db/pull/943#discussion_r3404188413_

Inspect the ignored network-accessing tests in the sedona-raster-zarr crate and review how tests are currently run. Compare the proposed options—unignoring them, moving network access to sedona-testing, or scheduling them less often—and document a chosen policy. Done means the tests have a defined, reliable execution path without unnecessary stress on external servers.

Written by the indexing model from the issue text.