[BOLT] Update section index for symbols from unemitted functions

Summary:
Under some conditions, e.g. while running in lite mode or when a
function is non-simple, BOLT may decide not to emit function code and
hence there's no need to update the symbol. However, since we change
section table, the corresponding section index may need an update.

Also, update section index for ICF symbols.

(cherry picked from FBD21970017)