Model an MFX module as the 135 mm slot that centres it, and add the NTR4 module

[BioCam]

An MFX module is 134 mm across and stands in a 135 mm carrier slot, which the track's sliding blocks centre it in. MFX_DWP_module_flat is modelled as 134 mm at the slot's origin rather than centred in it, so a plate on it sits 0.5 mm left of where it stands.

Modelled as the 135 mm its slot is, a plate centred on the module is centred on the slot.

plate on MFX_DWP_module_flat, MFX carrier at track 30	x
on main today	755.62
with this PR	756.12

• hamilton_mfx_module_tiprackholder_ntr (cat. no. 191425) is the NTR4 site, for a stack of up to four 96 nested tip racks. 135 mm across for the same reason, 94 mm deep from Hamilton's NTR4Module model, 20 mm tall measured.
• The carrier's height reads 18.2 rather than 18.195 throughout. It cancels between the carrier's site and each module's own height, so nothing on the other three modules moves; on MFX_DWP_module_flat, whose height is independent of it, it is 5 um.
• The 0.5 mm comes from the geometry, not from a run recorded on an instrument as the tip positions in Correct MFX carrier sites by y-=0.5 mm, rename MFX_TIP_module and make it an EmbeddedTipRackHolder #1275 did.

Tests: the NTR module centres an SBS rack over its slot. Full suite 3409 passed, 4 skipped, on pytest 9.0.3 and 9.1.1 both. make lint, make format-check and typos clean.

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