entities summoned relatively to the player don't have the correct coordinates

Verification builds: 1.16.20.50 Release build, 1.14.60 Release build

Summary: When summoning an entity on the player, the entity has a slight offset to the player.

Impact: In general this is a very big deal, coordinates are messed up with a non-negligible offset. This also affects precise operations using the player coordinates, this can be very problematic in specific mini-games. This also goes against parity with Java, where this doesn't happen.

Reproduction steps:

1. type "/summon armor_stand"
2. notice how the armor_stand is not located at the exact coordinates of the player

Expected result

The entity is summoned precisely at the player's position.

Actual result

The entity is summoned with a slight offset to the player's position.