[Codegen] Apply bounds to subgroup_id

[krzysz00]

Since we're fixing to start using subgroup_id more often with PCF, apply bounds to it based on the subgroup size (or sizes) and the number of threads in the workgroup. Also extend subgroup_size handling to account for known subgroup sizes instead of giving up completely when there isn't a fixed choice made yet.

Also fix up some double-spaces in test attributes.

[amd-eochoalo]

I think this looks good, but you may want to wait for other reviewers. Just one comment about the for-loop.

[amd-eochoalo]

Nit: I think this is a little bit more difficult to parse than it should be. Could we remove one level of nesting by moving the break earlier and then the else should not be necessary, right? Maybe changing the logic slightly too for calculating the maxTotalThreads when target is known and avoid overflow somehow or adding variables?

// pseudocode

Suggested change

	for (std::optional<int64_t> size : workgroupSizes) {
	if (size) {
	maxTotalThreads *= *size;
	// Cap at the hardware thread-per-workgroup limit inside the loop
	// to avoid overflow from multiplying per-dimension maximums.
	if (target) {
	maxTotalThreads =
	std::min(maxTotalThreads,
	static_cast<int64_t>(
	target.getWgp().getMaxThreadCountPerWorkgroup()));
	}
	} else {
	allSizesKnown = false;
	break;
	}
	// if target is available
	std::optional<int64_t> maxThreadCountPerWg = static_cast<int64_t> (target.getWgp().getMaxThreadCountPerWorkgroup()));
	for (std::optional<int64_t> size : workgroupSizes) {
	if (!size) {
	allSizesKnown = false;
	break;
	}
	maxTotalThreads *= *size;
	// Cap at the hardware thread-per-workgroup limit inside the loop
	// to avoid overflow from multiplying per-dimension maximums.
	if (maxThreadCountPerWg) {
	maxTotalThreads = std::min(maxTotalThreads, maxThreadCountPerWg)
	}
	}