app-benchmarks/filebench: eapi bump, add new use flag, fix dependencies

app-benchmarks/filebench: eapi bump, add new use flag, fix dependencies

The following changes have been made:
- eapi bump to EAPI 6
- drop unused inherit eutils
- remove unsued dependency on libaio: the program uses the aio functions
  defined in libc. libaio is not referenced in the source code.
- remove the automagic dependency on dev-libs/libtecla: filebench
  provides tab-completion support using libtecla. However, there's no
  way to explicitly control it. Patch the sources to add a configure
  option for '--with-libtecla' and add a corresponding USE flag called
  'auto-completion'.
- drop parallel compilation workaround: the package compiles with
  different values of '-j' successfully. Most likely a carry-over from
  the initial ebuild.

Package-Manager: portage-2.2.26