Fix for CI docker builds.

[bitner]

The docker image for pgstac has four targets.

• pgstacbase: This target is essentially the same as postgis/postgis with pgtap, plpgsql-check, and partman installed (which are used for testing/development, but not required for using pgstac), it is a base postgres/postgis image that is ready to install pgstac, but does not have it installed yet.
• pgstacbase-plrust: This is the pgstacbase image that also has PLRUST installed in preparation for future development (PLRUST is not used yet).
• pgstac: This target is the pgstacbase image with pgstac already installed at a specific version
• pgstac-rust: This target is the pgstacbase-plrust image with pgstac already installed at a specific version

CI ran into issues with building the pgstacbase-plrust and pgstac-plrust targets. This PR does three things:

• Update the pgstacbase-plrust target with the latest PLRUST version
• Modify the CI release to push the pgstacbase and pgstac targets rather than the PLRUST targets as PLRUST is not used yet.
• Update the incremental migration tests to start at v0.3.0 rather than v0.1.9 due to a breaking change in pg_partman at version 5 that has no ability to pin a version.

[vincentsarago]

@bitner can we add those comments in https://github.com/stac-utils/pgstac/blob/main/.github/workflows/continuous-integration.yml#L48 and also add platforms: linux/amd64,linux/arm64