[BUG] Index pattern service returns inconsistent title

[ashwin-pc]

Describe the bug

The index pattern service updated the cached index pattern title to contain the datasource title in it, but this behaviour is not consistent and calling the get method on the index pattern service shows only the saved object title without the datasource in title. This leads to inconsistent behaviour in the UI.

https://github.com/opensearch-project/OpenSearch-Dashboards/blob/2.16/src/plugins/data/common/index_patterns/index_patterns/index_patterns.ts#L124-L135

To Reproduce
Steps to reproduce the behavior:

1. Call indexPatterns.getIdsWithTitle()
2. Call indexPatterns.get(id) // any id from the previous list
3. Compare the titles

Expected behavior
Instead of modifying the cache, we shoud store the datasource title as well if we want to avoid another call for the datasource and only append it where we display it to the user. We should ideally never modify the raw title attribute since without it we no longer know what the index pattern title was without making a raw call to the saved object service.

OpenSearch Version
2.16

Dashboards Version
2.16

Plugins

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Screenshots

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Host/Environment (please complete the following information):

• OS: [e.g. iOS]
• Browser and version [e.g. 22]

Additional context

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