Skip sfn->sfn context injection when CONTEXT field exists (case 2)

[lym953]

What does this PR do?

If the Parameter.Input field has custom CONTEXT, then skip context injection and print a warning. This case should be rare, so we don't support this case for now. We can consider supporting it if a client actually complains.

Motivation

Testing Guidelines

Passed the added test

Additional Notes

See all the cases in the design doc Fixing Step Function Instrumentation

Types of changes

• [ ] Bug fix
• [x] New feature
• [ ] Breaking change
• [ ] Misc (docs, refactoring, dependency upgrade, etc.)

Check all that apply

• [x] This PR's description is comprehensive
• [ ] This PR contains breaking changes that are documented in the description
• [ ] This PR introduces new APIs or parameters that are documented and unlikely to change in the foreseeable future
• [ ] This PR impacts documentation, and it has been updated (or a ticket has been logged)
• [x] This PR's changes are covered by the automated tests
• [ ] This PR collects user input/sensitive content into Datadog

[lym953]

/merge

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[dd-devflow[bot]]

:steam_locomotive: MergeQueue: pull request added to the queue

The median merge time in main is 2m.

Use /merge -c to cancel this operation!