ld: Add tests for -z separate-code and -z noseparate-code
    
    Verify that -z separate-code works and -z noseparate-code doesn't disable
    -z relro.
    
    	PR ld/22393
    	* testsuite/ld-elf/pr16322.d: Add -z noseparate-code.
    	* testsuite/ld-elf/pr22393-1.s: New file.
    	* testsuite/ld-elf/pr22393-1a.d: Likewise.
    	* testsuite/ld-elf/pr22393-1b.d: Likewise.
    	* testsuite/ld-elf/pr22393-1c.d: Likewise.
    	* testsuite/ld-elf/pr22393-1d.d: Likewise.
    	* testsuite/ld-elf/pr22393-1e.d: Likewise.
    	* testsuite/ld-elf/pr22393-1f.d: Likewise.
    	* testsuite/ld-elf/pr22393-2a.c: Likewise.
    	* testsuite/ld-elf/pr22393-2a.rd: Likewise.
    	* testsuite/ld-elf/pr22393-2b.c: Likewise.
    	* testsuite/ld-elf/pr22393-2b.rd: Likewise.
    	* testsuite/ld-elf/shared.exp: Run tests for -z separate-code.