Some blocks use an inconsistent brightness gamma in blocks.json

Although these oddities were always present, the fix for MCPE-167836 in 1.20.60.22 allows all of the brightness_gamma values in blocks.json to be changed, having a direct effect on the appearance of blocks in-game. This has both exposed new issues, and made older ones easier to fix. The fix for MCPE-167836 was correct and should not be reverted.

List of affected blocks:

• Sand, Red Sand - Brighter, inconsistent with Suspicious Sand (Fixed in 1.21.50.25)
• Sandstone, Red Sandstone and all of their variants - Updated: Single Sandstone Slab don't have the component "ambient_occlusion_exponent" : 0.70 set like the rest of the block set. Red Sandstone blocks are fully fixed in latest preview (Almost fixed in 1.21.50.25)
• Snow Block and Snow Layer - Brighter, regression of MCPE-57022
• Nether Brick - Slightly brighter, inconsistent with all of its variants (fixed in 1.21.50.25)
• Red Nether Brick and Red Nether Brick Stairs - Inconsistent with the slab and wall versions (fixed in 1.21.50.25)
• Oak, Birch, Spruce, Jungle, Acacia, Dark Oak and Mangrove Leaves - Slightly brighter, probably intentional
• Obsidian - Slightly darker, probably intentional
• Crying Obsidian and Glowing Obsidian - No effect in-game due to MCPE-177349

A simple fix for these would be to set these blocks' brightness_gamma component in blocks.json to the default value, which is 1. (Creator: You can also just delete the "ambient_occlusion_exponent" component from the block)