(Drupal) Keep resource limits in sync with php.ini

[mhavelant]

Currently:

• Resource limits can be set via values.yaml
• PHP limits can be set via env

Problem:

• One needs to keep track of these and adjust them in tandem

Solution proposal:

• Memory limit should be mapped to the php.ini config value
  • Currently, the usual env var is PHP_MEMORY_LIMIT, that should be auto-set
  • (Later) Allow specifying the memory limit env var
  • (Later) Allow setting a different limit

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Additionally, stuff like ingress request timeout and max_execution_time (+ possibly others) should probably be set up like this, too (with the same 'allow overrides' method).