* Mw/lambda envoy extension parse region (#4107)
* updated builtin extension to parse region directly from ARN
- added a unit test
- added some comments/light refactoring
* updated golden files with proper ARNs
- ARNs need to be right format now that they are being processed
* updated tests and integration tests
- removed 'region' from all EnvoyExtension arguments
- added properly formatted ARN which includes the same region found in the removed "Region" field: 'us-east-1'
* regenerated proto files
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