Proposal: Add support Nacos SD config

[dongjiang1989]

Proposal

Add support Nacos SD config.

Prometheus will periodically check the REST endpoint and create a target for every app instance.

The following meta labels are available on targets during relabeling:

• __meta_nacos_app_name: the name of the app
• __meta_nacos_app_instance_id: the ID of the app instance
• __meta_nacos_app_instance_hostname: the hostname of the instance
• __meta_nacos_app_instance_homepage_url: the homepage url of the app instance
• __meta_nacos_app_instance_statuspage_url: the status page url of the app instance
• __meta_nacos_app_instance_healthcheck_url: the health check url of the app instance
• __meta_nacos_app_instance_ip_addr: the IP address of the app instance
• __meta_nacos_app_instance_vip_address: the VIP address of the app instance
• __meta_nacos_app_instance_secure_vip_address: the secure VIP address of the app instance
• __meta_nacos_app_instance_status: the status of the app instance
• __meta_nacos_app_instance_port: the port of the app instance
• __meta_nacos_app_instance_port_enabled: the port enabled of the app instance
• __meta_nacos_app_instance_secure_port: the secure port address of the app instance
• __meta_nacos_app_instance_secure_port_enabled: the secure port of the app instance
• __meta_nacos_app_instance_country_id: the country ID of the app instance
• __meta_nacos_app_instance_metadata_<metadataname>: app instance metadata
• __meta_nacos_app_instance_datacenterinfo_name: the datacenter name of the app instance
• __meta_nacos_app_instance_datacenterinfo_<metadataname>: the datacenter metadata

[roidelapluie]

HTTP SD support was added in version 2.2.0 of Nacos: https://nacos.io/zh-cn/blog/2.2.0-release.html