Add more inputs to maxscale-enterprise-docker release workflow

The workflows for building docker images at maxscale-enterprise-docker were not quite sufficient for 25.10.3 and 25.10.3-trial.

The buildnumber of 25.10.3 had to be bumped, but currently it is not possible to specify the buildnumber from the UI. To accomodate that, a hardwired fix was created in the branches mxs-25103-2-standard and mxs-25103-2-all-python3.13. Both branched from the obvious ones.

When building the docker image of the MaxScale trial version, a -trial must be injected into the download path. To accomodate that, a hardwired fix was created in the branch mxs-25103-trial, branched from mxs-2510-full-python3.13.

These fixes should be made unnecessary by appropriate extending the choses you can make in the default branches.

Further, when building from ci-repository, the subdirectory must be specified. In the UI, that should be moved up right after the place where you select between ci-repository and release-repository. If possible, the subdirectory entryfield should be shown only if ci-repository is chosen.