(U+5C70): Add `<-denotational@usage' for A2-DJT-02521; add

(U+5C70): Add `<-denotational@usage' for A2-DJT-02521; add
`sound@ja/on/{kan|go}'.
(UU+5C70): Unify DJT-02521; add some relations for other characters.
(A-IWDSU+21636-itaiji-001): New abstract node.
(A-U+21636-itaiji-001): New abstract node; use `<-denotational' for
A-IWDSU+21636-itaiji-001.
(U+21636-itaiji-001): New character; use `<-denotational' for
A-U+21636-itaiji-001.
(U-00021D1C): Apply new conventions for glyph granularity.
(A-IWDSU+21D1E): New abstract node.
(U-00021D1E): Use `->denotational' and `->subsumptive'; add
`<-denotational' for A-IWDSU+21D1E.
(A2-DJT-02521): New abstract node.