[perf] Avoid using property for simple attributes to reduce python overhead.

[ailzhang]

Stack from ghstack:

• -> [perf] Avoid using property for simple attributes to reduce python overhead. #3910
• [opengl] Respect max_block_dim in ti.init #3909

This is a part of cprofile result when I profile python launch
overhead for ndarray kernels. Note how dtype/n/m/shape queries takes up a
lot of time in extract_args. These are indeed caused by property which
is super slow. We should just make them normal attributes to speed
things up.

This PR reduces the time we spent at extract_args from 1.6s to 1.01s
in my profiled use case.

Reference:
https://stackoverflow.com/questions/21174590/property-speed-overhead-in-python

Note that I didn't get rid of all properties here, there're still some
low hanging fruit like element_shape.

/home/ailing/github/taichi/python/taichi/lang/kernel_impl.py:252(extract_arg)                                        ->  600000    0.344    0.451  /home/ailing/github/taichi/python/taichi/lang/_ndarray.py:53(dtype)
                                                                                                                         400000    0.150    0.150  /home/ailing/github/taichi/python/taichi/lang/_ndarray.py:251(shape)
                                                                                                                         200000    0.102    0.102  /home/ailing/github/taichi/python/taichi/lang/matrix.py:1325(n)
                                                                                                                         200000    0.086    0.086  /home/ailing/github/taichi/python/taichi/lang/matrix.py:1329(m)
                                                                                                                         200000    0.104    0.104  /home/ailing/github/taichi/python/taichi/lang/matrix.py:1333(shape)
                                                                                                                         600000    0.351    0.351  /home/ailing/github/taichi/python/taichi/lang/matrix.py:1397(n)
                                                                                                                         600000    0.335    0.335  /home/ailing/github/taichi/python/taichi/lang/matrix.py:1401(shape)
                                                                                                                         600000    0.088    0.088  /home/ailing/github/taichi/python/taichi/types/annotations.py:33(check_element_dim)
                                                                                                                         400000    0.034    0.034  /home/ailing/github/taichi/python/taichi/types/annotations.py:39(check_layout)
                                                                                                                         600000    0.064    0.064  /home/ailing/github/taichi/python/taichi/types/annotations.py:45(check_element_shape)
                                                                                                                         600000    0.061    0.061  /home/ailing/github/taichi/python/taichi/types/annotations.py:51(check_field_dim)
                                                                                                                        2300000    0.153    0.153  {built-in method builtins.isinstance}
                                                                                                                        1200000    0.076    0.076  {built-in method builtins.len}
/home/ailing/github/taichi/python/taichi/lang/kernel_impl.py:300(extract)                                            ->  600000    1.655    3.709  /home/ailing/github/taichi/python/taichi/lang/kernel_impl.py:252(extract_arg)
                                                                                                                         600000    0.053    0.053  {method 'append' of 'list' objects}

[qiao-bo]

Thanks!

[qiao-bo]

After reading the post and some other info, it seems like when the getter/setter has some logic required, using the property decorator is preferred. Only the simple ones do not require and will have overhead. So maybe element_shape will not be improved as much as these simple ones. Lets see if property is still bottleneck after this PR ;)

[strongoier]

LGTM!

[k-ye]

Yay