make_1020_channel_selections should have option to get names (not just indices)

Feature request: Allow retrieval of channel names (not only indices) via `make_1020_channel_selections()`, e.g. by adding a new parameter `return_ch_names`

_Originally posted by @hoechenberger in https://github.com/mne-tools/mne-python/pull/11596#discussion_r1148592874_
            