Added support for categorized groups and commands in helptext output

[pymergetic]

• Added CommandCategory decorator to helptext module for marking a method with a category
• Added fire_category for classes to enable categorization
• Everything that has no categorization goes into groups/command by default
• Added helper functions to retrieve action groups by name and to list groups between specified names.
• Updated _GetActionsGroupedByKind to support dynamic action groups based on categories.
• Refactored _UsageDetailsSections to utilize new grouping logic for better organization of help text sections.

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