XMover: Improve connection configuration for port-forwarding scenarios

[coderabbitai]

Context

@WalBeh expressed a wish for better configuration variables suitable for port-forwarding scenarios when using XMover.

Suggested Configuration Variables

The following configuration variables would be helpful for port-forwarding setups:

CRATE_CONNECTION_STRING=https://localhost:4200/
CRATE_USERNAME="crate"
CRATE_PASSWORD=""
CRATE_SSL_VERIFY="false"
PYTHONHTTPSVERIFY=0
PYTHONWARNINGS="ignore:Unverified HTTPS request"

Background

This came up during the development of XMover in PR #523, where the current connection configuration in cratedb_toolkit/admin/xmover/database.py could be enhanced to better support port-forwarding scenarios commonly used in development and testing environments.

Acceptance Criteria

• Enhance XMover's connection configuration to better support port-forwarding scenarios
• Ensure SSL verification can be easily disabled for local development
• Support suppressing HTTPS warnings for development scenarios
• Document the configuration options for port-forwarding use cases

References

• Original PR: Admin/XMover: Add CrateDB shard analyzer and movement tool #523
• Comment thread: Admin/XMover: Add CrateDB shard analyzer and movement tool #523 (comment)

/cc @WalBeh