CLOUDP-266431: Add the output transformation logic to foascli (skeleton)

[andreaangiolillo]

Proposed changes

Jira ticket: CLOUDP-266431

This PR proposes the following changes:

• moves the changelog.go from openapi package to its own package
• defines a outputfilter package which will contains all the transformations for the entries
• adds the message transformations

./bin/foascli changelog create -b ~/Downloads/test/base -r ~/Downloads/test/revision -e ~/Downloads/test/exceptions.yaml                                         
Printing the checks
{
  "id": "api-schema-removed",
  "text": "removed the schema 'AzureHardwareSpec20250101'",
  "level": 3,
  "section": "components"
}
{
  "id": "endpoint-added",
  "text": "endpoint added",
  "level": 1,
  "operation": "GET",
  "operationId": "getVersion",
  "path": "/rest/unauth/version",
  "source": "/Users/andrea.angiolillo/Downloads/test/revision/v2.json",
  "section": "paths"
}
....