[gdb/testsuite] Fix gdb.ada/access_tagged_param.exp for aarch64

[gdb/testsuite] Fix gdb.ada/access_tagged_param.exp for aarch64

On aarch64-linux, I run into:
...
Breakpoint 2, pck.inspect (obj=0x430eb0 \
  <system.pool_global.global_pool_object>, <objL>=0) at pck.adb:17^M
17         procedure Inspect (Obj: access Top_T'Class) is^M
(gdb) FAIL: gdb.ada/access_tagged_param.exp: continue
...
while on x86_64-linux, I see:
...
Breakpoint 2, pck.inspect (obj=0x62b2a0, <objL>=2) at pck.adb:19^M
19            null;^M
(gdb) PASS: gdb.ada/access_tagged_param.exp: continue
...
Note the different line numbers, 17 vs 19.

The difference comes from the gdbarch_skip_prologue implementation.

The amd64_skip_prologue implementation doesn't use gcc line numbers, and falls
back to the architecture-specific prologue analyzer, which correctly skips
past the prologue, to address 0x4022f7:
...
00000000004022ec <pck__inspect>:
  4022ec:       55                      push   %rbp
  4022ed:       48 89 e5                mov    %rsp,%rbp
  4022f0:       48 89 7d f8             mov    %rdi,-0x8(%rbp)
  4022f4:       89 75 f4                mov    %esi,-0xc(%rbp)
  4022f7:       90                      nop
  4022f8:       90                      nop
  4022f9:       5d                      pop    %rbp
  4022fa:       c3                      ret
...

The aarch64_skip_prologue implementation does use gcc line numbers, which are:
...
File name                    Line number    Starting address    View    Stmt
pck.adb                               17            0x402580               x
pck.adb                               17            0x402580       1       x
pck.adb                               19            0x40258c               x
pck.adb                               20            0x402590               x
...
and which are represented like this internally in gdb:
...
INDEX  LINE   ADDRESS            IS-STMT PROLOGUE-END
0      17     0x0000000000402580 Y
1      17     0x0000000000402580 Y
2      19     0x000000000040258c Y
3      20     0x0000000000402590 Y
4      END    0x00000000004025a0 Y
...

The second entry is interpreted as end-of-prologue, so 0x402580 is used, while
the actual end of the prologue is at 0x40258c:
...
0000000000402580 <pck__inspect>:
  402580:       d10043ff        sub     sp, sp, #0x10
  402584:       f90007e0        str     x0, [sp, #8]
  402588:       b90007e1        str     w1, [sp, #4]
  40258c:       d503201f        nop
  402590:       d503201f        nop
  402594:       910043ff        add     sp, sp, #0x10
  402598:       d65f03c0        ret
  40259c:       d503201f        nop
...

Note that the architecture-specific prologue analyzer would have gotten this
right:
...
(gdb) p /x aarch64_analyze_prologue (gdbarch, pc, pc + 128, 0)
$2 = 0x40258c
...

Fix the FAIL by making the test-case more robust against problems in prologue
skipping, by setting the breakpoint on line 19 instead.

Likewise in a few similar test-cases.

Tested on x86_64-linux and aarch64-linux.