feat: add node label on elasticsearch_nodes_roles metric

[pincher95]

This pull request updates the Elasticsearch nodes roles metric to include the unique node ID as a label. This provides better identification and disambiguation of nodes with the same name or host, improving the accuracy of monitoring and troubleshooting. The change is reflected in both the metric generation code and the corresponding test cases.

Metrics and Labeling Improvements:

• Added a new node label (containing the node ID) to the elasticsearch_nodes_roles metric, updating the defaultRoleLabels array in collector/nodes.go to include "node".
• Modified the collection logic to use the node ID as a label value when emitting the elasticsearch_nodes_roles metric. [1] [2]

Testing Updates:

• Updated test cases in collector/nodes_test.go to expect the new node label in all elasticsearch_nodes_roles metric outputs, ensuring tests accurately reflect the new metric format. [1] [2] [3]

[pincher95]

resolves #1105