Set required frequency config in Crystal test files

[akhilles]

Note

Low Risk
Small, localized change to generic component parameter configuration and its tests; main risk is compatibility if any callers relied on config_unit parsing behavior.

Overview
Crystal.zen switches frequency (required) and load_capacitance (optional) from config_unit(...) to plain config(...), changing how these unit-typed parameters are parsed/validated.

test_Crystal.zen is updated to explicitly pass frequency="16MHz" when instantiating both 2-pin and 4-pin crystals so the tests continue to generate components with the required parameter set.

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