Backporting SQS: Support JSON format to moto-3.1.18

[ziyanli-amazon]

This is the exact same commit that fixes Issue
This commit is based off tag 3.1.18
Just back-porting this PR to version 3.1.18

[bblommers]

Hi @ziyanli-amazon! We don't support Moto 3.x anymore - we only develop for the current version.

Are you running into any issues upgrading to 4.x?

[ziyanli-amazon]

@bblommers Hi, the reason for this PR is that we still have some internal customers who depend on 3.x. No, there's no issue for 4.x.
Is there any other way we can patch the 3.x version ?

[bblommers]

Hi @ziyanli-amazon, I've just released 3.1.19. It contains this change, plus a few others that were necessary to get our internal tests to pass.

https://pypi.org/manage/project/moto/release/3.1.19/

Just to make sure this doesn't generate any expections:
My earlier statement still stands - We don't support Moto 3.x anymore - we only develop for the current version..

The decision to release this version was more curiosity then anything else, to see how much effort it would take.

Like I said, (almost) all of our internal tests pass against this version, but let me know if you run into any issues.

This is the PR with all the changes: #7042