Use New Architecture Client by Default in TiCDC Binary

[wlwilliamx]

Description

Currently, the TiCDC binary defaults to using the old architecture client, but the new architecture introduces additional configurations that do not exist in the old architecture. As a result, using the old architecture client with the new architecture binary can lead to errors due to missing configurations.

Since the new architecture client is fully compatible with the old architecture, we should modify the TiCDC binary to always use the new architecture client. This change will prevent configuration mismatches while maintaining backward compatibility.

However, for cdc server, we will continue to support both the new and old architectures, with the old architecture remaining the default. Users can still enable the new architecture in the same three ways as before:

1. Adding the --newarch (or -x) flag when running cdc server
2. Setting the environment variable: export TICDC_NEWARCH=true
3. Specifying newarch: true in the server configuration file

Acceptance Criteria:

• Modify the TiCDC binary to always use the new architecture client
• Ensure cdc server continues to support both architectures with the old one as the default
• Users can still enable the new architecture for cdc server using the existing three methods