Namespaces and tags can be inconsistent across wikis:
>>! In T378179#10263684, @Urbanecm wrote:
> In this output, namespaces 250-253 belong to ProofreadPage, and only exist at Wikisources. Specifically with ProofreadPage, namespaces defined by this extension have //different IDs// at different wikis. For example, the same four namespaces at `sourceswiki` are NS104-107. This happens to avoid conflict of namespace IDs on per-wiki basis.
Given this, filtering on all namespaces would be similarly inconsistent and/or confusing, as filters would be dependent on the wiki generating the form. Instead, we should only filter on namespaces and tags we know to be constant across all wikis which are the namespaces returned by `NamespaceInfo::getCommonNamespaces()` and the tags returned by `ChangeTagsStore::getSoftwareTags` respectively.