Update image used in CI-tests from ubuntu:18.04 to ubuntu:22.04 to avoid deprecation problems

[Zombaya]

Ubuntu 18.04 is being deprecated in GitHub Actions since 8/8/2022 and will be fully unsupported by 4/1/2023.

To generate awareness, there are a couple of brown-out-periods where all CI-tests using that image will fail.

This merge-request will avoid any more possible failing CI-tests because of usage of a deprecated image.

Extra commits

1. Update Aws\Test\CloudFront\SignerTest::testBadPrivateKeyPath()

The message thrown by OpenSSL changed from version 1.x (used in ubuntu 18.04) to version 3.x (used in ubuntu 22.04).

I only modified the test to capture this new error message. Since both outputs are rather cryptic, I think we can improve the developer experience when Signer::__construct() throws a proper message to signal the provided keyfile is incorrect, and appended, the original error-message from OpenSSL.

I did not modify this now to restrict changes only related to the test-image.

2. Add more output-logging when Tests\Crypto\Polyfill\AesGcmTest::testCompat() fails

This tests is rather flaky and randomly fails. Previously it only showed the result of both encryptions, which does not allow reproduction of the error.

I've added a failure-message which shows the input used, so we can reproduce the test-case the next time this flaky test fails again.

I'm aware this is not strictly related to the test-image-update, so I can split this off to a seperate PR, but as the change has no impact on the actual code or changes any tested codepaths, I thought it was acceptable to add this to this PR.

# Sample output
Failed with parameters:
	plaintext: ea98e4dcd86f0787e08f169ba7225d2e5921fff6...
	aad: c377dee941af1f9210e3cbd96718637a8fe446a551a83182c0...
	key: d2ff5fde9f2ce01af2cec3fee052e691f272bfac5d80e78efc3f74969c1fcb86
	nonce: aac1ca71959724f547fc9245
Failed asserting that two strings are identical.
Expected :04be5db843e1acd76413ff1214cdea22aa  (appended some text to cause test to fail)
Actual   :04be5db843e1acd76413ff1214cdea22

Postscript

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[yenfryherrerafeliz]

Hi @Zombaya, thanks for this contribution. Would you please be able to do a rebase on this PR?

Thanks!