Expose PrimitiveMesh's request_update method

[jsjtxietian]

Fixes #89067

[jsjtxietian]

Looks like the function under callable_mp, create_custom_callable_function_pointer uses template as instance type and function type, so it can't deduce the parent/child relation and I have to use static_cast to cast the type and make it compile.

[akien-mga]

Thanks!

[jsjtxietian]

I just found out this is my 100th commit to godot repo (althoung most of them are trivial), thanks for all of your help along the way :)