Merge remote-tracking branch 'remotes/stsquad/tags/pull-for-6.2-041121-2' into staging

Testing, gdbstub and plugin updates for 6.2

 - add microblaze and nios2 compiler docker images
 - fix test cross compiler detection for some targets
 - don't try and link ebf to user targets
 - add L2 tracking to cache plugin
 - exit cleanly on C-a x
 - clean up debug output in check-tcg
 - switch to thread on break in gdbstub
 - update openbsd VM to 7.0

# gpg: Signature made Thu 04 Nov 2021 08:14:35 AM EDT
# gpg:                using RSA key 6685AE99E75167BCAFC8DF35FBD0DB095A9E2A44
# gpg: Good signature from "Alex Bennée (Master Work Key) <alex.bennee@linaro.org>" [full]

* remotes/stsquad/tags/pull-for-6.2-041121-2:
  tests/vm/openbsd: Update to release 7.0
  tests/tcg: remove debug polluting make output
  gdbstub: Switch to the thread receiving a signal
  tests/tcg: remove duplicate EXTRA_RUNS
  plugins: try and make plugin_insn_append more ergonomic
  tests/plugins: extend the insn plugin to track opcode sizes
  chardev: don't exit() straight away on C-a x
  docs/tcg-plugins: add L2 arguments to cache docs
  plugins/cache: make L2 emulation optional through args
  plugins/cache: split command line arguments into name and value
  plugins/cache: implement unified L2 cache emulation
  plugins/cache: freed heap-allocated mutexes
  ebpf: really include it only in system emulators
  tests/tcg: enable debian-nios2-cross for test building
  tests/docker: split PARTIAL into PARTIAL and VIRTUAL images
  tests/tcg: Fix some targets default cross compiler path
  tests/tcg: Enable container_cross_cc for microblaze
  tests/docker: Add debian-microblaze-cross image
  tests/docker: Add debian-nios2-cross image

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>