docs/interop: convert text files to restructuredText

docs/interop: convert text files to restructuredText

buglink: https://gitlab.com/qemu-project/qemu/-/issues/527
Signed-off-by: Souleymane Conte <conte.souleymane@gmail.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-id: 20250522092622.40869-1-conte.souleymane@gmail.com
[PMM: switched a few more bits of formatting to monospaced;
 updated references to qcow2.txt in MAINTAINERS, qcow2-cache.txt
 and bitmaps.rst]
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>