Api4 - Use explicit adder functions rather than magicMethod

[colemanw]

Overview

Improves the way some Api4 action classes receive their parameters.

Before

Api Actions had been relying on a magic method to provide getter/setter functions for params.
That works fine for simple get/set operations but it was also attempting to provide adder functions.
Those are more nuanced and the magic method didn't do a good job of understanding whether the param was an indexed or unindexed array, and didn't do strict type checking.

After

Making our own adder functions gives better documentation, stricter checking of inputs and also
the convenience of variadic functions for adding several values at once.
Magic "addFoo" removed.

[civibot]

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[colemanw]

@seamuslee001 the checkStyle test doesn't understand docblocks for variadic functions. I'm using the recommended @param Type ...$var docs which is supported by PHPStorm. Do you think we could either:

1. Upgrade our style checker to see if it's been fixed upstream
2. Patch it ourselves
3. Just disable those specific checks

[seamuslee001]

@colemanw looks like we might need to apply a patch from here https://www.drupal.org/project/coder/issues/2878783 Likely patch 5 i would imagine

[seamuslee001]

@colemanw have created a PR here civicrm/coder#9

[seamuslee001]

Jenkins re test this please

[eileenmcnaughton]

Our unit test cover should be pretty solid on this