[NNC] Fix masking for all block and thread dimensions in CudaCodeGen (#44733)
Summary:
Unifies a number of partial solutions to the thread and block dimension extent masking, including the NoThreadIdxWriter and my last fix https://github.com/pytorch/pytorch/issues/44325. The NoThreadIdxWriter is gone in favour of tracking the current loop extents and masking any statements that have a lower rank than the launch parameters in any Block or Thread dimension, which handles both the "no" and "smaller" axis binding cases.
For example it will transform the following:
```
for i in 0..10 // blockIdx.x
for j in 0..10 // threadIdx.x
do thing(i, j);
for k in 0..5 // threadIdx.x
do other thing(i, k);
```
Into:
```
do thing(blockIdx.x, threadIdx.x);
if (threadIdx.x < 5) {
do other thing(blockIdx.x, threadIdx.x);
}
```
And handle the case where statements are not bound by any axis, eg.
```
do outer thing;
for i in 0..10 // blockIdx.x
for j in 0..10 // threadIdx.x
do thing(i, j);
do other thing(i);
```
will become:
```
if (blockIdx.x < 1) {
if (threadIdx.x < 1) {
do outer thing;
}
}
syncthreads();
do thing(blockIdx.x, threadIdx.x);
syncthreads();
if (threadIdx.x < 1) {
do other thing(blockIdx.x);
}
```
Pull Request resolved: https://github.com/pytorch/pytorch/pull/44733
Reviewed By: mruberry
Differential Revision: D23736878
Pulled By: nickgg
fbshipit-source-id: 52d08626ae8043d53eb937843466874d479a6768
