Enable oPPUlance support in pynn-brainscales

See merge request technical-coordination/project-internal/devops/platform/ebrains-spack-builds!101

We can drop oppulance from `spack.yaml` as it is no top-level
dependency anymore.

(BSS-2 features embedded SIMD processors for plasticity and other use
cases. This prepares for the next pynn-brainscales update adding
some code-generation features.)

Upgrade oPPUlance (cross compiler for BrainScaleS-2's embedded "PPU" processor)

See merge request technical-coordination/project-internal/devops/platform/ebrains-spack-builds!99

This reverts merge request !87

Update PyNN

See merge request technical-coordination/project-internal/devops/platform/ebrains-spack-builds!87

Added biobb-md

See merge request technical-coordination/project-internal/devops/platform/ebrains-spack-builds!93

Fix py-torch: Enable tensorpipe

See merge request technical-coordination/project-internal/devops/platform/ebrains-spack-builds!96

Add py-frites

See merge request technical-coordination/project-internal/devops/platform/ebrains-spack-builds!97

Add py-viziphant

See merge request technical-coordination/project-internal/devops/platform/ebrains-spack-builds!91

Add py-elephant

See merge request technical-coordination/project-internal/devops/platform/ebrains-spack-builds!90

Add py-neo

See merge request technical-coordination/project-internal/devops/platform/ebrains-spack-builds!86

Add py-quantities

See merge request technical-coordination/project-internal/devops/platform/ebrains-spack-builds!85

Importing torch yields an ImportError caused by some mismatch between
build options (distributed is enabled, but tensorpipe is not →
this seems unsupported → enable tensorpipe).

Related to: https://support.humanbrainproject.eu/#ticket/zoom/14319

Fix oppulance: Explicitly depend on modern flex version

See merge request technical-coordination/project-internal/devops/platform/ebrains-spack-builds!95

Fix oppulance

See merge request technical-coordination/project-internal/devops/platform/ebrains-spack-builds!94

If starting from scratch the archive file isn't there in do_fetch;
in this case, we can make use of the folder where the freshly
downloaded resources are cloned to.

Add oPPUlance (the SDK for the embedded processors (aka PPUs) on BrainScaleS)

See merge request technical-coordination/project-internal/devops/platform/ebrains-spack-builds!73