Port diagrams to drawio. Update with eval_ast/macro changes.

This incorporates various updates to the diagrams.
* The largest change is the incorporation of the new process where
  eval_ast is integrated into eval and the macroexpand function and has
  been incorporated directly into the eval TCO loop and no longer
  requires a separate function or special form. For the most part, this
  change was discussed in #587 and
  implemented in #592. Instead of
  a special form, there is now a "apply macro" box in the eval block.
  The "apply macro" box has a TCO line (but not env creation line unlike
  the "apply" box.
* Change the "eval_ast" sub-block to "evaluate" and convert the list of
  evaluated items to individual blocks. Add a "list" block and connect
  this to the "apply" block (rather than connecting eval_ast to eval).
* Change the "symbol lookup" arrow to point to the "symbol" box in the
  "evaluate" block instead of pointing to the "evaluate" block.
* Update the "create env" arrows to point to the child env box instead
  of the root/REPL env box.
* Add try/catch TCO line.
* Remove the `or` macro and `gensym` function from stepA since this has
  been dropped for a while.

README.md

@@ -33,7 +33,7 @@ that are new for that step are highlighted in red.
 Here is the final architecture once [step A](process/guide.md#stepA)
 is complete:
 
-![stepA_mal architecture](process/stepA_mal.png)
+![stepA_mal architecture](process/steps.png)
 
 If you are interested in creating a mal implementation (or just
 interested in using mal for something) you are welcome to to join our