Add decrypt option to cache:view command

[cmuench]

Magerun pull-request check-list:

• Pull request against develop branch (if not, just close and create a new one against it)
• README.md reflects changes (if any)
• phar fuctional test (in tests/phar-test.sh)

Fixes #1254

Changes proposed in this pull request:

• Add decrypt option
• Use Magento standard Decryptor

[github-actions]

Download the artifacts for this pull request:

• n98-magerun2.phar.zip

[cmuench]

@damienwebdev Did some experimental tests by including the standard encryptor.

n98-magerun2.phar cache:view --decrypt --unserialize SYSTEM_SCOPES

prints this on my dev machine:

{
    "websites": {
        "admin": 1,
        "0": 1,
        "base": 1,
        "1": 1
    },
    "stores": {
        "admin": 1,
        "0": 1,
        "default": 1,
        "1": 1
    }
}

Sadly n98-magerun2.phar cache:view --decrypt --unserialize SYSTEM fails, because of some data in the cache.

[cmuench]

Found the issue in some data of the "application_key".

[cmuench]

Seems that not alle config values are "json encodable". So we should skip the --unserialize option there. I see currently now way to handle that automatically.
The new version will print a hint and the Json Exception Message.