Make a test farm tests package (#8821)

Fixes https://github.com/certbot/certbot/issues/8781.

This PR makes our test farm tests into a normal package so it and its dependencies can be tracked and installed like our other packages.

Other noteworthy changes in this PR:

* Rather than continuing to place logs in your CWD, they're placed in a temporary directory that is printed to the terminal.
*  `tests/letstest/auto_targets.yaml` was deleted rather than renamed because the file is no longer used.

* make a letstest package

* remove deleted deps

* fix letstest install

* add __init__.py

* call main

* Explicitly mention activating venv

* rerename file

* fix version.py path

* clarify "this"

* Use >= instead of caret requirement

letstest/README.md

@@ -0,0 +1,65 @@
+# letstest
+Simple AWS testfarm scripts for certbot client testing
+
+- Launches EC2 instances with a given list of AMIs for different distros
+- Copies certbot repo and puts it on the instances
+- Runs certbot tests (bash scripts) on all of these
+- Logs execution and success/fail for debugging
+
+## Notes
+  - Some AWS images, e.g. official CentOS and FreeBSD images
+    require acceptance of user terms on the AWS marketplace
+    website.  This can't be automated.
+  - AWS EC2 has a default limit of 20 t2/t1 instances, if more
+    are needed, they need to be requested via online webform.
+
+## Installation and configuration
+
+This package is installed in the Certbot development environment that is
+created by following the instructions at
+https://certbot.eff.org/docs/contributing.html#running-a-local-copy-of-the-client.
+
+After activating that virtual environment, you can then configure AWS
+credentials and create a key by running:
+```
+>aws configure --profile <profile name>
+[interactive: enter secrets for IAM role]
+>aws ec2 create-key-pair --profile <profile name> --key-name <key name> --query 'KeyMaterial' --output text > whatever/path/you/want.pem
+```
+Note: whatever you pick for `<key name>` will be shown to other users with AWS access.
+
+When prompted for a default region name, enter: `us-east-1`.
+
+## Usage
+To run tests, activate the virtual environment you created above and from this directory run:
+```
+>letstest targets/targets.yaml /path/to/your/key.pem <profile name> scripts/<test to run>
+```
+
+You can only run up to two tests at once. The following error is often indicative of there being too many AWS instances running on our account:
+```
+NameError: name 'instances' is not defined
+```
+
+If you see this, you can run the following command to shut down all running instances:
+```
+aws ec2 terminate-instances --profile <profile name> --instance-ids $(aws ec2 describe-instances --profile <profile name> | grep <key name> | cut -f8)
+```
+
+It will take a minute for these instances to shut down and become available again. Running this will invalidate any in progress tests.
+
+A temporary directory whose name is output by the tests is also created with a log file from each instance of the test and a file named "results" containing the output above.
+The tests take quite a while to run.
+
+## Scripts
+Example scripts are in the 'scripts' directory, these are just bash scripts that have a few parameters passed
+to them at runtime via environment variables.  test_apache2.sh is a useful reference.
+
+test_apache2 runs the dev venv and does local tests.
+
+See:
+- https://docs.aws.amazon.com/cli/latest/userguide/cli-chap-getting-started.html
+- https://docs.aws.amazon.com/cli/latest/userguide/cli-ec2-keypairs.html
+
+Main repos:
+- https://github.com/letsencrypt/letsencrypt