[inductor] Stop using `x + tl.zeros(...)` in generated triton (#100163)
For reductions, this changes the accumulator
```python
_tmp2 = tl.zeros([XBLOCK, RBLOCK], tl.int8) + -128
```
to
```python
_tmp2 = tl.full([XBLOCK, RBLOCK], -128, tl.int32)
```
which is equivalent since addition does type promotion from `int8` to `int32`
For constant indexing, this changes
```python
tl.store(in_out_ptr0 + (0 + tl.zeros([XBLOCK, 1], tl.int32)), tmp4, None)
```
to
```python
tl.store(in_out_ptr0 + (tl.full([XBLOCK, 1], 0, tl.int32)), tmp4, None)
```
For variable indexing, this changes
```python
tl.store(out_ptr0 + (0 + tl.zeros([XBLOCK], tl.int32)), tmp1, None)
```
to
```python
tl.store(out_ptr0 + (tl.broadcast_to(x0, [XBLOCK])), tmp1, None)
```
Pull Request resolved: https://github.com/pytorch/pytorch/pull/100163
Approved by: https://github.com/ngimel
