Convert code-review-guide.md to rst

Convert code-review-guide.md to rst

Convert titles as approproate.

Use inter-doc references for other full docs.  Convert other external
links to RST-style references, keeping the labels (3-F).  One
exception to this: sphinx noticed that there were two 'D' labels;
rename one to `Shift Left`.

Convert internal link to RST-style reference.

 Add spaces so that lists compile correctly.

Remove explicit HTML <br> tags; Make them a separate block to achieve
a similar goal.

Convert "manual" **subsubsection** sections to RST subsubsuctions
(^^^^^).

No textual changes.

Signed-off-by: George Dunlap <george.dunlap@citrix.com>