Add global entry with before script to new CI config

What does this MR do?

This MR adds a new entries to a new CI config class. It is next refactoring step after !4462 (merged).

See #15060 (closed)

I will rebase on top of master after !4462 (merged) is merged.

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• 7f2f683e - Rename ci config module that holds nodes to Node

Marked this merge request as a Work In Progress

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• 8048dcc8 - Implement CI configuration nodes tree processing

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• 251dd571 - Extract CI config validation helpers to mixin

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• cc558f3e - Validate new before script CI configuration entry

mentioned in issue #17686 (closed)

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• 6dbd1c86 - Validate new before script CI configuration entry

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• 1ff8725d - Collect errors from all nodes in new CI config

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• a3c07455 - Collect errors from all nodes in new CI config

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• e23705a0 - Use CI config errors from new processor in legacy one

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• 940763e0 - Use CI config errors from new processor in legacy one

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• b95c60a0 - Do not process Ci config node when node is a leaf

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• 69a3755c - Add Ci config entry that implements Null Object

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• e8f995ef - Pass root Ci config entry to each subsequent entry

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• 6bd67f52 - Do not process new Ci config entry when invalid

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• df25c196 - Use Ci config validation helpers only where needed

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• c2d6d61d - Add DSL for adding nodes in Ci config interface

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• 70bda3e8 - Implement script in Ci config and use in legacy one