[Adityakk9031]

When defining ArrayOf or HashOf with nil?: true (e.g. ArrayOf[String, nil?: true]), #coerce accepts nil elements and records exactness appropriately.

However, case equality (===) did not take nilable? into account:

• In ArrayOf, other.all?(item_type) evaluated item_type === nil, which returned false.
• In HashOf, pattern matching only looked for in [Symbol | String, ^type], similarly rejecting nil values.

This caused === pattern matching and variant matching in Union#dump to fail whenever arrays or hashes contained nil items.

Updated ArrayOf#=== and HashOf#=== to permit nil elements when nilable? is true, and added unit tests in base_model_test.rb.

cc @contextualbeer

[Adityakk9031]

Hi @contextualbeer, whenever you have a chance, could you please take a look at this PR? Thank you!