[klippa] make the glyph closure signatures match in GSUB and cmap/glyf/COLR?

There is already a trait `GlyphClosure` defined for in GSUB, and I added glyph closure for cmap and glyf tables in #983, should we make the signatures match?
By a quick look, it seems that the glyph closure I added has a input unicodes set, and we compute transititve closure for glyphs in this set only, while the closure in current GSUB table computes all reachable glyphs in the whole table.

Start by comparing the existing GSUB `GlyphClosure` trait with the glyph-closure implementations for cmap and glyf added in #983, and check how COLR participates. Determine whether the input-unicode behavior and whole-table reachable-glyph behavior should share one signature, then define the agreed completion criteria and add or update tests for the resulting closure semantics.

Written by the indexing model from the issue text.