feat: nebula graph add time label

[waleedalzarooni]

Description

I have incorporated a time dimension into the Nebula graph knowledge graph implementation. I have modified the ensure_tag_exists method, ensure_edge_type_exists, add_node, add_triplet and get_structured_schema methods to include time dimensions according to this Nebula graph documentation https://docs.nebula-graph.io/3.8.0/3.ngql-guide/3.data-types/4.date-and-time/.

Motivation and Context

I have added these changes in so that Nebula graph knowledge graphs can be used to create a financial dynamic knowledge graph as in this paper, https://arxiv.org/pdf/2407.10909.
If it fixes an open issue, please link to the issue here, #1172

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• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds core functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
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• Example (update in the folder of example)

Implemented Tasks

• Subtask 1
• Subtask 2
• Subtask 3

Checklist

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• I have updated the tests accordingly. (required for a bug fix or a new feature)
• I have updated the documentation accordingly.

[Wendong-Fan]

Thanks @waleedalzarooni for the contribution! I believe we need to confirm whether the string for the time is validated. The time label is not meant to indicate when the tag was created but rather to serve as a property label. This label should be optional, and if the user does not provide it, this should not be set. I will add one more commit based on your work, thanks again for the contribution and happy new year!