Blender Git Loki

Fix T54339: Shapekey Max value doesn't clamp existing value

Update the "current value" of the Shape Key blend amount when value is
not within the min/max range. New function `rna_ShapeKey_update_minmax`
used to update and clamp the current value.

Reviewed By: mano-wii, lichtwerk, #animation_rigging, sybren

Maniphest Tasks: T54339

Differential Revision: https://developer.blender.org/D11071