Add DLOPEN macros that stamp the caller's ELF and use it to ensure executables list...

Currently almost all the dlopens happen in libbasic or libshared code,
so the ELF dlopen notes all end up in libsystemd-shared. Many
distributions split this library and various binaries in separate
packages, and the library ends up with soft-dependencies, even though
many binaries are either completely useless or do not work at all with
the dlopen dependency. This also makes it impossible to know which
executable uses which dlopen dependency without inspecting the source
code.

If someone only wants to add the soft dependencies from libshared they
can just avoid parsing the executable binaries. By design the code in
libbasic/libshared still does the stamping too, at lower priorities, so
that libsystemd-shared will always list all the optional dependencies,
and if one wants to build a minimal system by default, they can just
parse libsystemd-shared dlopen notes, and ignore the individual
executables. But for many distribution the current setup is insufficient
and requires adding a ton of manual library dependencies, as many
executables become effectively broken or useless without the dlopen
dependencies installed (eg: resolved fails to start without libssl,
repart can do basically nothing without blkid, etc).

Add a new set of DLOPEN_<LIB> macros that wrap the dlopen_lib and also
pull in the ELF note voodoo, so that the callers get their ELF binaries
stamped too. Convert a bunch of callers to use the macro, and use
`required` dependencies for the callers that do not work without the
dlopen library being available.

The one caveat is that, in order to avoid duplicating the exact same
note in a binary due to multiple call sites, some `asm` voodoo is done
instead of the previous bare-C section-creating macro. The drawback of
this approach is that if `--gc-sections` is used to link the binary (as
we do), then binutils >= 2.36 is required for the `SHF_GNU_RETAIN` flag.
This effectively cuts off CentOS 9, so what I did here is adding an
override in meson to detect missing support, and drop `SHF_GNU_RETAIN`.
The build works, but on CentOS 9 there's no dlopen ELF notes anymore.
Given it's just that version, and it goes EOL next year, that seems ok
to me. The alternative is to drop the usage of `--gc-sections` on CentOS
9, or to accept duplicated notes everywhere, and both seem worse.

End result:

```
$ readelf --notes build/systemd-executor

Displaying notes found in: .note.gnu.property
  Owner                Data size 	Description
  GNU                  0x00000010	NT_GNU_PROPERTY_TYPE_0
      Properties: x86 ISA needed: x86-64-baseline

Displaying notes found in: .note.gnu.build-id
  Owner                Data size 	Description
  GNU                  0x00000014	NT_GNU_BUILD_ID (unique build ID bitstring)
    Build ID: 8a0c3db54adb79ae54e1432255011aa4ab583742

Displaying notes found in: .note.ABI-tag
  Owner                Data size 	Description
  GNU                  0x00000010	NT_GNU_ABI_TAG (ABI version tag)
    OS: Linux, ABI: 3.2.0

Displaying notes found in: .note.dlopen
  Owner                Data size 	Description
  FDO                  0x0000006b	FDO_DLOPEN_METADATA
    Dlopen Metadata: [{"feature":"pam","description":"Support for LinuxPAM","priority":"recommended","soname":["libpam.so.0"]}]
  FDO                  0x0000007c	FDO_DLOPEN_METADATA
    Dlopen Metadata: [{"feature":"seccomp","description":"Support for Seccomp Sandboxes","priority":"recommended","soname":["libseccomp.so.2"]}]
  FDO                  0x00000090	FDO_DLOPEN_METADATA
    Dlopen Metadata: [{"feature":"bpf","description":"Support firewalling and sandboxing with BPF","priority":"recommended","soname":["libbpf.so.1","libbpf.so.0"]}]
  FDO                  0x000000a0	FDO_DLOPEN_METADATA
    Dlopen Metadata: [{"feature":"cryptsetup","description":"Support for disk encryption, integrity, and authentication","priority":"recommended","soname":["libcryptsetup.so.12"]}]
  FDO                  0x00000078	FDO_DLOPEN_METADATA
    Dlopen Metadata: [{"feature":"mount","description":"Support for mount enumeration","priority":"recommended","soname":["libmount.so.1"]}]

$ readelf --notes build/systemd

Displaying notes found in: .note.gnu.property
  Owner                Data size 	Description
  GNU                  0x00000010	NT_GNU_PROPERTY_TYPE_0
      Properties: x86 ISA needed: x86-64-baseline

Displaying notes found in: .note.gnu.build-id
  Owner                Data size 	Description
  GNU                  0x00000014	NT_GNU_BUILD_ID (unique build ID bitstring)
    Build ID: dcd4568842e32da3e71be27db3def51c6b459994

Displaying notes found in: .note.ABI-tag
  Owner                Data size 	Description
  GNU                  0x00000010	NT_GNU_ABI_TAG (ABI version tag)
    OS: Linux, ABI: 3.2.0

Displaying notes found in: .note.dlopen
  Owner                Data size 	Description
  FDO                  0x00000075	FDO_DLOPEN_METADATA
    Dlopen Metadata: [{"feature":"mount","description":"Support for mount enumeration","priority":"required","soname":["libmount.so.1"]}]
  FDO                  0x00000072	FDO_DLOPEN_METADATA
    Dlopen Metadata: [{"feature":"selinux","description":"Support for SELinux","priority":"recommended","soname":["libselinux.so.1"]}]
```

diff --cc src/core/main.c
Simple merge

diff --cc src/shared/libarchive-util.c
Simple merge