Improve enrichment process performance

[zhquan]

This commit improves the performance of the enrichment process.

• Reduce the number of requests to get the backend name (_connecto_name).
• Reduce the number of queries to get information from SortingHat.
• Removes an unused method called get_uuid.
• Refactor and rename the __fix_field_date method to __cast_str_to_datetime to convert str to datetime and fix possible date format errors. With this method we reduce the number of calls of the str_to_datetime method.
• In the __add_commit_meta_fields method it only creates a new identity when it doesn't exist in SortingHat.
• In the add_identity method, remove the update_profile mutation; this is no longer necessary as we are using GraphQL.

[coveralls]

Pull Request Test Coverage Report for Build 5488832218

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 261 unchanged lines in 4 files lost coverage.
• Overall coverage decreased (-0.01%) to 82.651%

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Files with Coverage Reduction	New Missed Lines	%
/home/runner/work/grimoirelab-elk/grimoirelab-elk/grimoire_elk/enriched/github.py	2	75.79%
/home/runner/work/grimoirelab-elk/grimoirelab-elk/grimoire_elk/enriched/sortinghat_gelk.py	44	80.63%
/home/runner/work/grimoirelab-elk/grimoirelab-elk/grimoire_elk/enriched/git.py	92	72.63%
/home/runner/work/grimoirelab-elk/grimoirelab-elk/grimoire_elk/enriched/enrich.py	123	73.61%
<!--	Total:	261		-->

Totals
Change from base Build 5400461112:	-0.01%
Covered Lines:	9166
Relevant Lines:	11090

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💛 - Coveralls