Remove `set_unconditionally` & `BeValue` #2912

Job	Run time
Rustfmt	1m 10s
Build GS and check the result	2m 45s
cargo check no std	1m 35s
resources/scripts/ots_test.sh	1m 7s
Clippy lints	1m 32s
cargo test fea-rs	58s
fontbe tests	51s
fontc tests	1m 16s
tests other than fontbe,fontc	2m 12s
	13m 26s

Provide feedback