When configuring PodTemplates or PodTemplateSteps, we have the possibility to set a strategy to merge Yaml Pod definitions.

By default, the Yaml merge strategy is set to Override and it is currently non-configurable. The current way of working leads some issue when merging "mandatory" config set at admin level like tolerations, if users does not add explicitly the Merge flag into their Jenkinsfile definition, it got removed as the default strategy is Override.

The purpose of this issue is to create a new Boolean flag"inheritYamlMergeStrategy" at PodTemplate and PodTemplateStep level. By default the flag is set to false to keep backward compatibility. If the flag is set to true, It will allow users to keep the parent Yaml merge strategy and avoid maintenance all the Jenkinsfile YAML definition. When this new flag is set, in each level of Yaml PodDefinition merging, if the Yaml merge strategy is not explicitly set, it will take the parent one. In the same way, if the inheritYamlMergeStrategy is not explicitly set at each level, we should take the parent one