[EAK-504] Limited Parsys: add functionality to limit parsys-like components child component count

[ala-n]

Feature Final Scope:

A clientlib is provided to address the maximum children limit for containers (e.g., parsys) using a custom cq:listener or the design/policy property. The client library decorates the INSERT action and monitors editable placeholders (e.g., newpar). When the limit is reached, the INSERT action is hidden and inactive, placeholders are disabled, and an additional data-max-children-marker attribute is applied to placeholders for visual appearance customization (such as a custom red message and hover state, provided out-of-the-box).

In addition to the JS API, the EAK annotation set has been expanded with the @MaxChildren annotation to declare the maximum children resolver cq:listener using component Java metadata.

Notes for the Current PR:

• The support for complex rules in the Java API is beyond the scope of the current issue.
• Documentation, except for JS/Java docs, is not included and will be provided via a sub-PR or separately.
• The policy-management and the new max-children functionality have been consolidated into a single eak.policy client library/module, as they will reuse the same logic for rule filtering.

Closes: #504

[smiakchilo]

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