Add periodic build of generate-conda-packages with no upload but dummy metapackages generation

[traversaro]

In the generate-conda-packages we have the options to do a test run with no upload but with the generation of dummy metapackages. This include the robotology-distro-all package, that depends on all packages of the superbuild. This is helpful to catch problems like the one discussed in https://github.com/robotology/robotology-superbuild/pull/1583#issue-2104945554 . However, at the moment this option is triggered manually, typically to debug PRs. It is automatically run only when a new release is done, but this is not sufficient to actually catch regressions due to changes in conda-forge pinning or changes in latest-releases yml.

Possible we can add a job to run manually, or perhaps a run on "update latest releases" PRs?