Rollup merge of #138670 - compiler-errors:remove-afidt, r=oli-obk

Remove existing AFIDT implementation

This experiment will need to be reworked differently; I don't think we'll be going with the `dyn* Future` approach that is currently implemented.

r? oli-obk

Fixes #136286
Fixes #137706
Fixes #137895

Tracking:
* #133119

Author: matthiaskrgr