Proposal: Add “Generic Lazy-Holder Singleton Registry” Design Pattern (Hybrid Singleton Factory + Initialization-on-Demand Holder Idiom)

[Hari-099]

I would like to contribute a new design pattern to the repository:
Generic Lazy-Holder Singleton Registry Pattern — a hybrid design combining:

1. Initialization-on-demand holder idiom (best-practice JVM lazy-loading singleton)

2. Generic Singleton Factory / Multiton Registry (one singleton instance per class)

3. Reflection-safe instance creation

4. Concurrent, thread-safe instance registry using computeIfAbsent

This pattern provides a type-safe, lazy-loaded, per-class singleton registry that does not require external frameworks (like Spring) and works purely through Java language mechanisms.