linux-perf: Build a single unversioned package of perf

It is no longer necessary to match the kernel version, as perf is
intended to gracefully degrade when kernel features are missing.

- Drop all version suffixes, and the metapackage.
- Move the non-metapackage control template to
  control.tools-unversioned.in.
- Drop recommendation of linux-base.
- Use dpkg-maintscript-helper symlink_to_dir to replace the previous
  /usr/share/doc/linux-perf symlink.  We can't use dh_maintscript for
  this as the symlink target to match must be generated dynamically.
- Use dpkg-divert to move linux-base's wrappers and avoid a conflict.
- Put the remaining changes from debian/tools-perf-version.patch in
  debian/tools-perf-perf-read-vdso-in-libexec.patch.