Update connector metadata schema with new features

[timtay-microsoft]

• Change the nesting structure to more closely mimic how model types are defined
  • For instance, now all event datapoint level metadata are nested within the event level metadata
• Re-shape destination fields to allow users to specify defaults relevant to each supportable destination (default TTL/retain/qos/expiry time on messages published for MQTT destination, default DSS key for BrokerStateStore destination)
• Make connector metadata doc specify the min/max number of supported events/datasets/streams/management groups/etc.
• Allow users to provide alternative names to our types like "event", "datapoint", etc.
  • OPC UA refers to "datapoints" as "tags", for instance
• Disallow undefined fields from a connector metadata doc

Most of this is a breaking change, so it also bumps the version of the connector metadata schema

[Copilot]

Pull Request Overview

This PR updates the connector metadata schema from version 2.0-preview to 3.0-preview, introducing new features for better destination configuration and model field specifications. The changes enhance the schema to support destination-specific defaults and provide more detailed validation for connector capabilities.

• Schema version bump to 3.0-preview with new destination configuration structure
• Introduction of expectedModelFields and modelLimits for better connector validation
• Restructuring of destination fields to include default values for MQTT and BrokerStateStore

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 4 comments.

File	Description
dotnet/samples/Connectors/EventDrivenTcpThermostatConnector/connector-metadata.json	Removes deprecated isEndpointTlsEnabled field
doc/akri_connector/minimal-example-connector-metadata.json	Updates schema version and adds new model field specifications with minimal configuration
doc/akri_connector/example-connector-metadata.json	Updates schema version and restructures destination configuration with comprehensive field definitions
doc/akri_connector/connector-metadata-schema.json	Defines the new 3.0-preview schema with destination defaults and field necessity definitions