Extension blocks that might reuse existing extension simulator parts

[martinwork]

Describe the bug

Arising from two extensions that depend on existing neopixel and servo extensions.
#6123 (comment)
#6121 (comment)

I created some examples with code in custom.ts.

Wrapping existing calls that would show simulator parts, in functions with parameters, causes the simulator to jump down, but no simulated part is shown.
https://makecode.microbit.org/_Ku2KqDDxcPD6

I discovered that it's easy to stop the simulator moving, and parts appearing, by adding, for example,
//% hiddenParts=microservo or //% hiddenParts="neopixel" to any block
https://makecode.microbit.org/_82tEEvb1sdtT

A block with no parameters triggers the servo to appear, but blocks with parameters still seem to have no effect on the simulation.
https://makecode.microbit.org/_2vXK82gF5U8s