Migrate process_manager_executables.settings to JSON

[dkarlovi]

Q	A
Bug report?	no
Feature request?	yes
BC Break report?	no
RFC?	no
Branch?	master

Currently, executable settings are stored as PHP serialized payloads. That means the database treats them as text and it's quite possible they become corrupted, which is exactly what happened in my case.

My suggestion is to migrate this field to MySQL's JSON data type. See https://github.com/pimcore/pimcore/issues/13359

Note: the symptom of this happening is getting

Process with id 212 not found

in the logs even though the executable exists. It can't unserialize the settings payload so the exception is assumed to be a "not found" type exception, but it isn't.