bug#28209: Add tests for Edebug

[Gemini Lasswell]

Hello,

Edebug didn't have any tests, so I wrote some. The tests focus on
Edebug's user interface for stepping through code and using breakpoints.
Parts of Edebug that these tests don't cover are the evaluation list
buffer, code coverage, and macro specifications.

The first of the two attached patches extends ert-with-message-capture
to catch the output of prin1, princ and print when it is destined for
the echo area. Edebug uses prin1 and princ to show the results of
evaluating expressions. I don't know why it uses them instead of
message, and if there isn't a good reason for it, then modifying Edebug
to use message instead of extending ert-with-message-capture is another
option. If someone with a better understanding than mine of the
difference between princ and message would like to take a look at it,
the relevant code is in edebug-eval-expression and at the end of
edebug-eval-defun.

0001-Catch-more-messages-in-ert-with-message-capture.patch
Description: Text document

0002-Add-tests-for-Edebug.patch
Description: Text document