Bring back top level category, to avoid empty matrix.duckdb_arch for …

[carlopi]

…completely skipped archs

Problem is that otherwise output for fully skipped arch categories would be not clear.

[carlopi]

With this PR it shows as:

* Linux linux_arm64
* MacOS ${{ matrix.duckdb_arch }}
* Windows windows_amd64
* Wasm ${{ matrix.duckdb_arch }}

vs current of:

* linux_amd64
* matrix.duckdb_arch
* windows_amd64
* matrix.duckdb_arch

I think better but not ideal. Unsure if there is a way to clean that up.

Maybe solution is have matrix have at least the duckdb_arch field always present, just for printing purposes (that requires changing the go matrix generation script).

[carlopi]

@smvv: do you have any opinion here?

[smvv]

the taskfile idea would allow us to do cross-platform steps without splitting the platform jobs into separate hardcoded CI jobs.

That allows merging all these jobs into one job that depends on the matrix entries, so all jobs are named properly instead of matrix.duckdb_arch when skipped. wdyt?

[carlopi]

Sure, it's this improving or we don't care? To me there is somewhat more info, but your call, I think either merge or close.