[subset] Use hb_subset_input_t inside of subset_options_t so that input defaults are shared between the library and cli.

selection of which name records to keep in the subset method.

no-desubroutinize option is disabled for now
code cleanup (esp. CFF1 width handling)
bug fixes & renaming

Newer compilers / language allows structs with constructor in union.
So, this was not actually testing anything.  Indeed, the recent
change in DISALLOW_COPY *is* making some of our types non-POD.
That broke some bots.

Just remove this since it wasn't doing much, and I'd rather have
DISALLOW_COPY.

Sorry for the noise, downstream custom builders.  Please adjust.

New API:
+hb_face_builder_create
+hb_face_builder_add_table

Part of fixing https://github.com/behdad/harfbuzz/issues/585

This reverts commit 80af2812, reversing
changes made to c442672e.