Change parameters to rust_range

Change parameters to rust_range

This changes the parameters to rust_range, making it more suitable for
reuse by the (coming) new expression code.  In particular, rust_range
no longer evaluates its subexpressions.  Instead, they are passed in.

gdb/ChangeLog
2021-03-08  Tom Tromey  <tom@tromey.com>

	* rust-lang.c (rust_range): Change parameters.
	(rust_evaluate_subexp): Update.