Add read-only Masakari Instance HA API support - #4068

For #3158

Add read-only support for Masakari's Instance HA v1 API so Go applications can inspect failover inventory and recovery activity through Gophercloud. This supports consumers such as OpenStack exporter without maintaining a separate HTTP implementation.
The change adds:

• NewInstanceHAV1(ctx, provider, endpointOpts), discovering the instance-ha service through the Keystone catalog.
• List and Get operations for failover segments and their hosts, notifications, and VM moves nested under notifications.
• Typed results, resource filters, sorting, and marker-based pagination using the numeric IDs expected by Masakari.
• Unit tests for service-client construction, resource reads, query serialization, pagination, and error responses.
• A read-only acceptance test covering inventory and available recent notification and VM move records.

Segment enabled is associated with API microversion 1.2; VM moves require 1.3. Callers select the microversion through ServiceClient.Microversion. This change does not implement create, update, delete, or recovery-trigger operations.

This PR targets main and follows its context-aware client constructor. A companion v2 implementation is available for a backport if maintainers want it. This is a scoped first implementation of #3158 rather than full Masakari API coverage.