Add testcases to verify that all SHT_NOTE sections with the same section
alignment are placed in a single PT_NOTE segment.
PR ld/23658
* testsuite/ld-elf/pr23658-1.d: New file.
* testsuite/ld-elf/pr23658-1a.s: Likewise.
* testsuite/ld-elf/pr23658-1b.s: Likewise.
* testsuite/ld-elf/pr23658-1c.s: Likewise.
* testsuite/ld-elf/pr23658-1d.s: Likewise.
* testsuite/ld-elf/pr23658-2.rd: Likewise.
* testsuite/ld-elf/pr23658-3.d: Likewise.
* testsuite/ld-elf/pr23658-3.s: Likewise.
* testsuite/ld-elf/pr23658-3.t: Likewise.
* testsuite/ld-elf/shared.exp: Run PR ld/23658 tests.