Allow usage of `Rg11b10Float` for HDR

## What problem does this solve or what need does it fill?

This potentially gives a huge performance boost on weaker mobile devices.

E.g. in my game, I just changed `ViewTarget::TEXTURE_FORMAT_HDR` from `Rgba16Float` to `Rg11b10Float` and fps increased from 70 to 100 on my Xiaomi Note 8 Pro (midrange phone from 2019). In SDR the fps was about 110. No other changes were required to make it work.

## What solution would you like?

It could be a simple feature flag or a more convenient but complicated to implement run time option.

This format seems to be pretty imprecise (https://bartwronski.com/2017/04/02/small-float-formats-r11g11b10f-precision/) so shouldn't be used all the time.

## What alternative(s) have you considered?

## Additional context

There was some discussion about this in Discord rendering-dev, and it turns out the HypeHype engine uses this format too for mobile perf.