LPD-46389 Rework data set serialization (filters)

[dsanz]

Continuation of #158684 where

• We inline as much as we can, to pack logic into bigger methods for scaling, minimizing the number of class attributes to those really shared.
• Review variable naming in tests so that i) everything has FDS in it and ii) we no longer use Impl in variables
• Defer variable declaration till it's used. This provides more cohesive units of logic inside big methods

[liferay-continuous-integration]

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[brianchandotcom]

@dsanz Please resend on top of dsanz#95

[dsanz]

see #158861