.github: speedup go/horizon workflow tests by disabling postgres fsync

[toqueteos]

What

The CI PostgreSQL shouldn't write to disk, this is accomplished by disabling fsync.

Why

The official Docker Hub postgres image doesn't expose an easy to use lever for this, bitnami/postgresql does.

This should speedup tests significantly, specially on GHA which has less than ideal I/O speeds.

Known limitations

N/A

[tamirms]

@toqueteos the CI checks were not successful

[toqueteos]

To be honest, not the results I was expecting.

Times have gone down (on Horizon workflow) by 2~10 minutes.

But surprisingly have gone up (on Go workflow).

Go (this one is worse)

Before: https://github.com/stellar/go/actions/runs/14062641693

After: https://github.com/stellar/go/actions/runs/14061580978

Horizon (this one is better)

Before: https://github.com/stellar/go/actions/runs/14055333167

After: https://github.com/stellar/go/actions/runs/14061580947