Move some utils for editor only.

[andy840119]

Because some of the utils are for editor only.
.
e.g: cut the lyric or change the text-tag index.

[andy840119]

Guess should be better to move those utils into the Objects namespace because:

1. Those utils not only use in the editor.
2. Those utils should not be global.

[andy840119]

Not very sure about this but guess the action like LyricsUtils.SplitLyric should still ok to become a part of utils?

Maybe should rename like GetSplittedLyric? Utils should act like get something, not "doing" something inside.

[andy840119]

This issue can be closed because Hit-object related utils (e.g. display time-tag info or split the lyric) will be moved into the Objects namespace.
see:
#2043

Utils in the Edit namespace only for the logic in the editor only(ui or non-ui).