chore: Refactor and add test for sfn->Lambda context injection when P…

[lym953]

…arameters is string

What does this PR do?

When the Parameters field of an "InvokeLambda" step is a string instead of an object, currently we skip context injection.

This PR:

1. refactors code by flipping if condition
2. print a warning message in this case
3. add a test case

Motivation

Testing Guidelines

Pass the added test

Additional Notes

Types of changes

• [ ] Bug fix
• [ ] New feature
• [ ] Breaking change
• [x] 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

[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!