Add closed positions to focal-plane and pupil mask wheels in METIS

[oczoske]

Add closed positions to the following filter wheels (with respective Polarion requirements):

• IMG_LM filter wheel (METIS-5284)
• IMG_LM ND filter wheel (METIS-5528)
• [IMG_LM PP wheel (METIS-3953) - "DARK-LM"] not implemented as we haven't defined a PP in IMG_LM
• IMG_N filter wheel (METIS_5348)
• IMG N ND filter wheel (METIS-5529)
• [IMG_N PP wheel (METIS-3954) - "DARK-N"] not implemented as we haven't defined a PP in IMG_N
• LMS-PP1 (METIS-3639) - pupil mask added to METIS_LMS.yaml
• [CFO-PP1 (METIS-5457)] not implemented as this would be primarily for (shaped) pupil masks. If needed, use metis['cold_stop'].update_transmission(0.) instead.

Notes:

• the transmission has to be set to a finite value so that a wavelength range can be determined. 1e-32 should be low enough.
• The pupil-mask wheel LMS-PP1 is implemented with this PR. It also includes two neutral-density settings, ND-2.8 and ND-1.4 (see also E-REP-ATC-MET-1003, v3-0, p.139). The actual pupil masks are currently only available in the WCU.

Closes #327

[oczoske]

Note: MOSAIC notebook test fails due to SVO timeout. Can be ignored.