ensure correct value for hasParams

[martin-mfg]

fix #21172
Turn hasParams from a field into a getter to ensure the value is always up to date.

The problem reported in #21172 was caused by not updating hasParams after removing some parameters. With the new design, such problems are not possible anymore for hasParams. We probably should apply the same change to other fields like e.g. hasRequiredParams as well.

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