Support GLboolean return type of WebGL2RenderingContext.getQueryParameter()

[leod]

WebGL2RenderingContext.getQueryParameter() returns GLboolean for QUERY_RESULT_AVAILABLE (see documentation). This PR adds support for mapping from GLboolean to u32 in get_query_parameter_u32().

As an alternative, I was considering to add get_query_parameter_bool(), but then realized that no other target has that method.

[grovesNL]

Thank you! Adding get_query_parameter_bool seems slightly preferable to me because the GLboolean result from glGetQueryObjectuiv could be handled the same way. What do you think?

[leod]

Sure! I think I'll close this PR then and would be happy to give adding get_query_parameter_bool() a try.

Hmm, thinking about this though, a few questions are coming to my mind:

1. My understanding is that, on native, get_query_parameter_u32() already works for QUERY_RESULT_AVAILABLE. Do we want to keep this behavior or make a breaking change? The latter might be hard to notice for users. If we choose the former, perhaps this PR would still be worth merging for consistency across targets.
2. Closely related -- how should the u32 / bool variants behave for parameters whose type does not match? Panic?