Fix seeking bug in AnimationPlayerEditor

[TokageItLab]

• Fixes [Animation] For existing animations, iterating to next/previous step does not update 'frame' or 'animation' properties of Animated Sprite #85129
• Fixes Animation Timeline Go to Next Step / Prev Step is triggering the wrong player->seek #83394

Since seek_delta() has gone, this kind of calculation should be no longer needed. (It is my bad, sorry for wrong porting)

• Supersedes / Closes Fix Animation Timeline Go to Next Step / Prev Step which triggered wrong animation display #83399

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• Fixes Looped animation uses value from the beginning when it shouldn't #37343
• Fixes Looped animation shows first frame if last one is selected. #85068

Since the loop is processed when actually seeking to the end, an epsilon value is subtracted on the editor so that it does not seek to the end; Floats cannot detect this epsilon value, so it should not affect the behavior of the editor.

• Supersedes / Closes Fix looped animation seek end. #85186

[SaracenOne]

Yeah, seems to address the issues and the implementation seems fine. LGTM 👍

[akien-mga]

Since it's editor code only, looks relatively safe to include now for 4.2-rc2, thus fixing the reported regressions.

[akien-mga]

Thanks!