Create static metadata to demonstrate attacks

[snahil28]

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Fixes issue #: Create static metadata that demonstrate attacks #360

Description of the changes being introduced by the pull request:
This pull request includes static metadata to simulate known attacks that TUF prevents, these can be fed to implementation to test if it handles the attacks appropriately.

Please verify and check that the pull request fulfils the following
requirements:

• The code follows the Code Style Guidelines
• Tests have been added for the bug fix or new feature
• Docs have been added for the bug fix or new feature

[jku]

The premise is great but I think the approach has flaws:

• this is a lot of generated data being stored in git, without info on how it was generated.
• Some of this data will become obsolete over time and debugging it is tricky (how could I tell if there was a copy-paste error already in the PR?)
• None of this data is being automatically tested for correctness
• there's a lot of example code in the documents. That code is not being tested

Any data in the repo must get tested automatically. In my opinion storing generated data is also wrong (publishing generated data is fine: the source of truth should be the scripts that generated the data). The PR is over a year old: I think it should be declined as it is, a better approach is required.

[joshuagl]

Closing this PR, a PR implementing the same premise with automated code would be very welcome.