Don't use acme.test_util outside of acme. (#7484)

`certbot-compatibility-test` is using code in `acme` that I proposed making private and not trivially importable in https://github.com/certbot/certbot/issues/5775.

To fix it, I switched to using Certbot's test utilities which I proposed keeping public to help with writing tests for plugins. When doing this I had to change the name of the key because `rsa1024_key.pem` doesn't exist in Certbot.

I also deleted the keys in `certbot-compatibility-test`'s testdata because because they are unused.

certbot-compatibility-test/certbot_compatibility_test/testdata/rsa1024_key.pem

@@ -1,15 +0,0 @@
------BEGIN RSA PRIVATE KEY-----
-MIICXAIBAAKBgQCsREbM+UcfsgDy2w56AVGyxsO0HVsbEZHHoEzv7qksIwFgRYMp
-rowwIxD450RQQqjvw9IoXlMVmr1t5szn5KXn9JRO9T5KNCCy3VPx75WBcp6kzd9Q
-2HS1OEOtpilNnDkZ+TJfdgFWPUBYj2o4Md1hPmcvagiIJY5U6speka2bjwIDAQAB
-AoGANCMZ9pF/mDUsmlP4Rq69hkkoFAxKdZ/UqkF256so4mXZ1cRUFTpxzWPfkCWW
-hGAYdzCiG3uo08IYkPmojIqkN1dk5Hcq5eQAmshaPkQHQCHjmPjjcNvgjIXQoGUf
-TpDU2hbY4UAlJlj4ZLh+jGP5Zq8/WrNi8RsI3v9Nagfp/FECQQDgi2q8p1gX0TNh
-d1aEKmSXkR3bxkyFk6oS+pBrAG3+yX27ZayN6Rx6DOs/FcBsOu7fX3PYBziDeEWe
-Lkf1P743AkEAxGYT/LY3puglSz4iJZZzWmRCrVOg41yhfQ+F1BRX43/2vtoU5GyM
-2lUn1vQ2e/rfmnAvfJxc90GeZCIHB1ihaQJBALH8UMLxMtbOMJgVbDKfF9U8ZhqK
-+KT5A1q/2jG2yXmoZU1hroFeQgBMtTvwFfK0VBwjIUQflSBA+Y4EyW0Q9ckCQGvd
-jHitM1+N/H2YwHRYbz5j9mLvnVuCEod3MQ9LpQGj1Eb5y6OxIqL/RgQ+2HW7UXem
-yc3sqvp5pZ5lOesE+JECQETPI64gqxlTIs3nErNMpMynUuTWpaElOcIJTT6icLzB
-Xix67kKXjROO5D58GEYkM0Yi5k7YdUPoQBW7MoIrSIA=
------END RSA PRIVATE KEY-----

certbot-compatibility-test/certbot_compatibility_test/testdata/rsa1024_key2.pem

@@ -1,15 +0,0 @@
------BEGIN RSA PRIVATE KEY-----
-MIICXAIBAAKBgQDCzejLjo8wsz0avrylt7HQyF0+vsKritF70EGmc64cV0XfkCTR
-o+vMXBXMuUY6Kv3hTXV7klgkNYmL7gXAsFGQ4B9qeMnkYn0GcQdI51u076y/26Fu
-37uJg45Q6eApKInJSsyLVMcAT4HUJ6fFnUodFAKR7vTzOQryNW7Et4gA4wIDAQAB
-AoGAKiAU40/krwdTg2ETslJS5W8ums7tkeLnAfs69x+02vQUbA/jpmHoL70KCcdW
-5GU/mWUCrsIqxUm+gL/sBosaV/TF256qUBt2qQCZTN8MbDaNSYiiMnucOfbWdIqx
-Zgls6GUoXQvPic9RUoFSlgfSjo5ezz6el5ihvRMp+wbk24ECQQD3oz4hN029DSZo
-Y3+flmBn77gA0BMUvLa6hmt9b3xT5U/ToCLfbmUvpx7zV1g5era2y9qt/o3UtAbW
-1zCVETgzAkEAyWHv/+RnSXp8/D4YwTVWyeWi862uNBPkuLGP/0zASdwBfBK3uBls
-+VumfSCtp0kt2AXXmScg1fkHdeAVT6AkkQJBAJb2XRnCrRFiwtdAULzo3zx9Vp6o
-OfmaUYrEByMgo5pBYLiSFrA+jFDQgH238YCY3mnxPA517+CLHuA5rtQw+yECQCfm
-gL/pyFE1tLfhsdPuNpDwL9YqLl7hJis1+zrxQRQhRCYKK16NoxrQ/u7B38ZKaIvp
-tGsC5q2elszTJkXNjBECQCVE9QCVx056vHVdPWM8z3GAeV3sJQ01HLLjebTEEz6G
-jH54gk+YYPp4kjCvVUykbnB58BY2n88GQt5Jj5eLuMo=
------END RSA PRIVATE KEY-----

certbot-compatibility-test/certbot_compatibility_test/util.py

@@ -8,13 +8,13 @@ import tarfile
 
 import josepy as jose
 
-from acme import test_util
+from certbot.tests import util as test_util
 from certbot import constants
 
 from certbot_compatibility_test import errors
 
 
-_KEY_BASE = "rsa1024_key.pem"
+_KEY_BASE = "rsa2048_key.pem"
 KEY_PATH = test_util.vector_path(_KEY_BASE)
 KEY = test_util.load_pyopenssl_private_key(_KEY_BASE)
 JWK = jose.JWKRSA(key=test_util.load_rsa_private_key(_KEY_BASE))