Rework CI to run tests locally using the VM-installed Postgres on all
target platforms.
### CI jobs
* Build release versions on Linux/Win/Mac and save build results as
output artifacts
* In a separate VMs (Linux/Win/Mac)
* use
[nyurik/action-setup-postgis](https://github.com/nyurik/action-setup-postgis)
to install postgis and run tests using the built artifacts
* run `cargo test` on Linux only
* copy built artifacts from the build step, and run tests using the
release martin binary
* package and publish if this is a release
### Other changes
* Port some minor changes from the rewrite to porting easier
* minor cleanups
* remove all "expected" data files - too unstable to be usable
