Release preparation v0.29.0/v0.0.26-alpha (#874)

CHANGELOG.md

aws/SDK_CHANGELOG.md

aws/sdk/aws-models/amplifybackend.json

aws/sdk/aws-models/apigateway.json

aws/sdk/aws-models/appconfig.json

aws/sdk/aws-models/appstream.json

aws/sdk/aws-models/auditmanager.json

aws/sdk/aws-models/backup.json

aws/sdk/aws-models/batch.json

aws/sdk/aws-models/chime.json

aws/sdk/aws-models/cloudtrail.json

aws/sdk/aws-models/connect.json

aws/sdk/aws-models/connectparticipant.json

aws/sdk/aws-models/databrew.json

aws/sdk/aws-models/datasync.json

aws/sdk/aws-models/devops-guru.json

aws/sdk/aws-models/dms.json

aws/sdk/aws-models/dynamodb.json

aws/sdk/aws-models/ec2.json

aws/sdk/aws-models/ecs.json