Add stubs for FrankenPHP #2139

Job	Run time
Run cs-fixer and stubs structure tests	7m 44s
Run tests against php 5.6	8m 3s
Run tests against php 7.0	9m 33s
Run tests against php 7.1	9m 52s
Run tests against php 7.2	9m 36s
Run tests against php 7.3	10m 31s
Run tests against php 7.4	10m 36s
Run tests against php 8.0	12m 11s
Run tests against php 8.1	12m 11s
Run tests against php 8.2	12m 10s
Run tests against php 8.3	12m 22s
Run tests against php 8.4	12m 8s
	2h 6m 57s

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