Support equality comparison for optional to non-optional (?T ==/!= T)

extracted function ir_try_evaluate_bin_op_const
extracted type_is_self_comparable function
renamed ir_try_evaluate_bin_op_const to ir_try_evaluate_bin_op_cmp_const
implemented analysis of ?T == T
added ir_set_cursor_at_end_and_append_basic_block_gen
use build_br_gen and ir_set_cursor_at_end_and_append_block_gen
added ir_append_basic_block_gen
removed include of all_types in ir.cpp
extracted compile-time and runtime evaluation of cmp_optional_non_optional to separate functions

closes #5390
closes #1332