WIP: add a basic top_k implementation

[ev-br]

Per data-apis/array-api#722

This is based on argsort, so should work for older, released numpies. The implementation is based on data-apis/array-api-compat#158, updated to match the spec of data-apis/array-api#722

A matching tests PR is data-apis/array-api-tests#438

[ev-br]

Needs a @requires_api_version('2026.12'), if that's indeed the version of the spec where top_k ends up being.

[betatim]

In case your conflicts are due to the recent update to ruff, try ruff check --fix --unsafe-fixes --ignore E402,E7,SIM117,SIM102,B023 --config "lint.isort.combine-as-imports=true" in your branch with ruff 0.16.1 to see if that resolves them. Top tip via #228 (comment)

[ev-br]

In case your conflicts are due to the recent update to ruff, try ruff check --fix --unsafe-fixes --ignore E402,E7,SIM117,SIM102,B023 --config "lint.isort.combine-as-imports=true" in your branch with ruff 0.16.1 to see if that resolves them. Top tip via #228 (comment)

Thanks! Tried the suggestion: it applied a host of changes and stopped at the same conflict. So I ended up resolving it in an old-fashioned way :-).