Fix the BFD library's find_nearest_line feature to produce consistent results.

 PR 30150
 * dwarf2.c (comp_unit_contains_address): Renamed to ... (comp_unit_may_contain_address): this,
 and added code to return true if the CU's ranges have not yet been computed.
 (_bfd_dwarf2_find_nearest_line_with_alt): Use the renamed function, simplifying code in the process.