docs/specs/rocker.txt: Convert to rST

docs/specs/rocker.txt: Convert to rST

Convert the rocker.txt specification document to rST format.  We make
extensive use of the :: marker to introduce a literal block for all
the tables and ASCII art, rather than trying to convert the tables to
rST table syntax.  This produces a valid rST document without needing
a huge diff.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20240801170131.3977807-2-peter.maydell@linaro.org