record and release old wgpu BindGroup items, which were otherwise not being released.

[rcoreilly]

Thanks to @AnyCPU for identifying leak and potential fix in #1434, and @StinkyPeach for reporting the issue.

Relevant to #1430

note that with screen zoom that there is a remaining issue associated with loading fonts for each different DPI size, which is not fixed with this PR, and will not be addressed until we do the vello and go-text refactor.

[rcoreilly]

I have now verified using the xcode instruments leak detector (had to turn system integrity protection off to run on go binaries) that this PR does fix the resizing memory leaks.

However, the special libwgpu_native.a library that I built using a PR to access a more recent wgpu version, which is NOT released in our webgpu package, does still leak surface textures. This library runs compute jobs significantly faster, but is not anything official, so hopefully they will come out with updated wgpu_native packages sometime soon, that actually work.

Even with the "good" released version of the wgpu_native library, there is an initial bump in memory usage at the point of first resizing, but it stabilizes from that point onward.

[kkoreilly]

LGTM overall, and the memory leak does seem to be gone for me when resizing, but there is still an unequivocal persistent memory leak when zooming the window in and out, which was the original report in #1430.

[kkoreilly]

Note that the same zooming memory leak appears to occur in #1434 as well. The fix could be a separate PR, but this PR then would not be a fix for #1430.

[rcoreilly]

it is the same situation as the resize:

an initial bump and then transients that re-stabilize. this plot from xcode leaks looks identical to resize.

[kkoreilly]

See #1430 (comment) for information about the remaining leaking when zooming.