Add a new command for annotating image digests for EOL

[NikolaMilosavljevic]

Contributes to: https://github.com/dotnet/docker-tools/issues/1201

The work is being split into smaller PRs to aid in review process.

Some notes:

• We allow two scenarios for annotations - with and without checking for existing annotations.
• Check for existing annotations relies on oras discover command and its stdout. This will likely be updated once Oras completed the work on managed library.
• oras login command was not needed, as we already do docker login
• We do not fail if we fail to annotate one digest, we proceed until the end and log all failures, at which point we fail the command.
• There are 3 tests right now. We could add more later.

JSON file format (with sample dates):

{
  "eolDate": "2024-05-27",
  "eolDigests": [
    {
      "digest": "digest-value"
    },
    {
      "digest": "digest-value",
      "eolDate" : "2022-03-01"
    }
  ]
}

EOL data can be specified as a global value (optional) for all digests in the file. Each digest can have its own specific EOL date, which overrides the global value (if set).

[dotnet-issue-labeler[bot]]

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[dotnet-issue-labeler[bot]]

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[NikolaMilosavljevic]

Hmm, some test failures on Linux. This worked fine on Windows.

Working on a fix.