Add idris2 tests

[ywata]

The intention of this commit is to add idris2 tests. That includes:

• add test2 as target in Makefile for idris2 test.
• When run idris2 test, idris-repl-history-file is set to ~/.idris2
• Added idris-tests2.el (this is copy of iris-tests.e) Because some of tests were failed.
• idris-test-utils.el is added for running commands in expected location
• Some easy test cases are added.
• iris-dump-events-to-file is added to dump event buffer
• In inferior-iris.el modified so that idris2's test succeeds. ("1) There was an issue in getting port number from ide-mode-socket. The implementation is not ideal because idris's warning seems ad hoc.
• added test3 as target in Makefile for newly added test cases for idris2. This might work for idris1 also but not implemented.

Consideration: I added test3 target for newly created test cases but it should be in test2. Originally, there were 5 test cases in idris-tests2.el failed. 4 of them were resolved by (*1) but it remains. It may because ProofSearch is missing but as I'm not sure, I left the test case as it is.

[jfdm]

This looks like some good work!

I have yet to look at it in detail, however, I will point out that I have just merge #533. This, coincidentally, introduced an idris-tests2.el as well. It would be great if you can rebase your branch off of master and address the issues. I expect, and want, that you will replace my idris-tests2.el with your own!

If you can do the rebase, I will then have a look at the PR in a bit more detail to see in their is anything that needs commenting on.

Thanks for the contribution, it is very much appreciated!

[jfdm]

Right, I didn't expect a new PR for this work. Sorry about that. Does this mean we can close this PR?