Validating whether metadata.json exists for each pattern, and reorganising pattern directories to support this

[dastra]

Description of changes:

Updated .github/metadata/metadata_json_validator.py to validate whether metadata.json exists for each test pattern directory, and to validate it. Where it does not or validation fails, comments on the PR.

Reorganised the /*-test-samples/ directories to allow for checks to be made. Standardised directory structure across languages.

Changes to metadata.json format:

• Twitter and linkedin ids in metadata.json are now the id rather than the full URL.
• pattern_source has an additional type of Partner
• Added optional pattern_source_name to describe which partner or customer the pattern came from

All metadata.json files comply with this format.

Files that have moved around:

Documentation:

• dotnet-test-samples/async-architectures/README.md and img/* have moved to dotnet-test-samples/README-ASYNC.md and img/
• typescript-test-samples/async-architectures/README.md has moved to typescript-test-samples/README-ASYNC.md

Patterns:

• dotnet-test-samples/async-architectures/async-lambda-dynamodb has moved to dotnet-test-samples/async-lambda-dynamodb
• dotnet-test-samples/async-architectures/async-lambda-sqs has moved to dotnet-test-samples/async-lambda-sqs
• typescript-test-samples/async-architectures/async-lambda-dynamodb has moved to typescript-test-samples/async-lambda-dynamodb

Created new metadata.json files for:

• java-test-samples/async-lambda-dynamodb/
• dotnet-test-samples/schema-and-contract-testing/

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[dastra]

I've checked a popular inbound link site and it doesn't report any inbound links to the async-architectures READMEs which were moved. And we'll amend the sync to serverlessland to ensure those patterns are still synchronised across OK