verification/rvgen: Restructure the classes to prepare for LTL inclusion

Both container generation and DA monitor generation is implemented in the
class dot2k. That requires some ugly "if is_container ... else ...". If
linear temporal logic support is added at the current state, the "if else"
chain is longer and uglier.

Furthermore, container generation is irrevelant to .dot files. It is
therefore illogical to be implemented in class "dot2k".

Clean it up, restructure the dot2k class into the following class
hierarchy:

         (RVGenerator)
              /\
             /  \
            /    \
           /      \
          /        \
    (Container)  (Monitor)
                    /\
                   /  \
                  /    \
                 /      \
              (dot2k)  [ltl2k] <- intended

This allows a simple and clean integration of LTL.

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Link: https://lore.kernel.org/692137a581ba6bee7a64d37fb7173ae137c47bbd.1751634289.git.namcao@linutronix.de


Reviewed-by: Gabriele Monaco <gmonaco@redhat.com>
Signed-off-by: Nam Cao <namcao@linutronix.de>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>