ceph.spec.in: use pkgconfig() for library BuildRequires

ceph.spec.in: use pkgconfig() for library BuildRequires

Library BuildRequires used per-distro -devel package names, some split
across %if suse / %if rhel branches only because the names differ. The
pkgconfig() virtual provides resolve identically on every rpm distro; the
spec already relies on them for fuse3, systemd and udev.

Switch every library dependency that ships a .pc to pkgconfig(), preserving
version constraints and feature guards. This collapses the suse-vs-rhel
naming splits (nss, keyutils, openssl, ldap, ibverbs, rdmacm, lz4, thrift,
libcryptopp) and the dedicated split blocks (nlohmann_json, lttng-ust,
babeltrace, expat) into single lines, and folds the duplicated xmlsec1 devel
packages together.

Left as package names: libaio and xfsprogs ship no reliable .pc; gperftools
carries version and tcmalloc-variant logic; numa is unconditional on rhel
but crimson-only on suse; and the xmlsec1 runtime backend plugins are
runtime test deps, not build-time pkgconfig() deps.

Signed-off-by: Kefu Chai <k.chai@proxmox.com>