feat: support indexName in dynamodb scaler

[Haegi]

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Fixes #4680

Relates to kedacore/keda-docs#1154

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[JorTurFer]

Hi,
I have a question from my DynamoDB ignorance xD
Does adding the value to DynamoDB stream make sense?

[Haegi]

Hi, I have a question from my DynamoDB ignorance xD Does adding the value to DynamoDB stream make sense?

Hi, I am not an DynamoDB streams expert but do they even offer something like a index value?
If yes, I am open to also contribute that in another PR.

[JorTurFer]

I have no idea 😅, that's why I asked.
Let's continue only with this and if anyone wants the value in the other scaler, they can contribute too 😁

[JorTurFer]

/run-e2e aws
Update: You can check the progress here

[JorTurFer]

Thanks for the improvement! ❤️