Increasing the maximum amount of field indices allowed

[AmesingFlank]

I found myself writing the this line of code yesterday:

            self.configuration_ids = ti.field(
                int, shape=(3, 4, 2, 3, 4, 2, 3, 4, 2, 3, 4, 2))

Of course, it didn't work because taichi currently constraints the maximum amount of indices to 8. Would it be possible to increase this limit to 12 or 16?

[AmesingFlank]

Created #6901 to increase this limit to 12, but please let me know if there are any concerns, or if you think we should go directly to 16.

[strongoier]

Increasing the limit to 12 is fine from my point of view.