Pick transparent renderables

[show50726]

Based on #6633 by @grassydragon, I continue to finish the requirements by @pixelflinger:

This is what I would like to see:

• have an option to include or not the transparents. I think there is value to not include the transparents in picking.
• reuse the structure pass in the case transparents are not included (each extra pass costs about the same as a shadow pass, it's not insignificant). Thanks to the framegraph design this can be done pretty easily: keep the old code, keep the new code and just select which "picking" resource you want to use based on wether transparents should be included -- the framegraph will take care of removing the pass that's not needed.

Here's what I did:

• Add a boolean in FView to select whether to pick transparent entities
• Use structure pass when the boolean is false, otherwise use a separate Picking Render Pass

Closes #6614

[grassydragon]

Hi @show50726!
Thank you for continuing working on this feature!