Execute running from command block instead of entity location

Release_466466

Summary:
When running an execute detect command from a command block, the command checks the detect location relative to the command block, not the entity.

Impact:
This basically makes the execute command useless. This will impact our current project (BLOZARK) by either removing a feature or reconstructing it in a much laggier way, which will impact performance across all devices.

Repro Steps:
1. Create a new world
2. Give yourself a repeating command block
3. Place the repeating command block on top of a quartz_block
4. Paste this command in the repeating command block: "execute @a ~ ~ ~ detect ~ ~-1 ~ quartz_block 0 effect @s speed 1 5 true"
5. Power the repeating command block
6. Note that you have the speed command despite not standing on a quartz_block
7. Break the quartz_block under the repeating command block and note that the effect is removed

Observed results:
The command is run from the location of the command block

Expected results:
The command should be run from every player

Screenshots/videos attached:
No