add Greengrass V2 IPC samples using new IPC-Client V2

[Kriechi]

Description of changes:

This PR adds new samples for Greengrass using the IPC Client V2.
See the included readme at samples/greengrass_v2/README.md for more details.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[sbSteveK]

This looks solid. Requesting some changes but they're up for debate if there's any disagreement.

• rename the greengrass_v2 folder to greengrass and restore the deleted sample and move it into that folder along with its .md readme file. Comments can be added that direct customers to v2 but since v1 is still here and may be in use, I'm not sure we want to remove existing resources yet.

• Update the samples/README.md to reflect moved old sample and include links to the readme to newly added greengrass v2 samples.

• change the README.md in the greengrass root samples folder to link to individual sample README.md files in each individual sample directory with instructions per sample written similarly to how the other samples have instructions on what they do and how to run. Shared setup/info can be placed in the root readme but it should be clear what is required and how to use each individual sample and any omitted setup information should be linked back to for ease of use.

• rename the code.py files to reflect the contents of the sample for clarity. The naming stucture of other samples should be used as a style guide. e.g. "greengrass_pubsub.py"

• Regarding recipes, our SDK supports Linux, MacOS, and Windows. If these components are expected to support the same, please rewrite them to include all platforms supported instead of exclusively linux or provide instructions in generating recipes the way the current ipc_greengrass.md does. If they do not support all three platforms, please explicitly include in the greengrass/README.md which platforms are supported to prevent customers who try to run the sample from being confused when following provided steps.

[Kriechi]

@sbSteveK to the first and second point: I did not delete any samples for GGv1 -- the file that shows up in the diff is already a GGv2 IPC sample, and I only renamed + moved it. Or do you mean a different one?

I'll take a look at your other points.

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