[gdb/tdep] Handle pipe2 syscall for amd64

[gdb/tdep] Handle pipe2 syscall for amd64

When running test-case gdb.reverse/pipe-reverse.exp on openSUSE Tumbleweed,
I run into:
...
(gdb) continue^M
Continuing.^M
Process record and replay target doesn't support syscall number 293^M
Process record: failed to record execution log.^M
^M
Program stopped.^M
0x00007ffff7daabdb in pipe () from /lib64/libc.so.6^M
(gdb) FAIL: gdb.reverse/pipe-reverse.exp: continue to breakpoint: marker2
...

The current glibc on Tumbleweed is 2.35, which contains commit
"linux: Implement pipe in terms of __NR_pipe2", and consequently syscall pipe2
is used in stead of syscall pipe.

There is already support added for syscall pipe2 for aarch64 (which only has
syscall pipe2, not syscall pipe), so enable the same for amd64, by:
- adding amd64_sys_pipe2 in enum amd64_syscall
- translating amd64_sys_pipe2 to gdb_sys_pipe2 in amd64_canonicalize_syscall

Tested on x86_64-linux, specifically on:
- openSUSE Tumbleweed (with glibc 2.35), and
- openSUSE Leap 15.3 (with glibc 2.31).

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=29056