feat: fetch term ID by term label

[nayib-jose-gloria]

Reason for Change

• 206

Changes

• add get_term_label_to_id_map to generate + return full term label to term ID maps by ontology_name, and cache them after they are generated once
• add get_term_id_by_label function to fetch single term IDs by their term label

Testing steps

• unit tests

Notes for Reviewer

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 85.54%. Comparing base (c493ca9) to head (a366428).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #212 +/- ## ========================================== + Coverage 85.26% 85.54% +0.28% ========================================== Files 18 18 Lines 1106 1128 +22 Branches 215 220 +5 ========================================== + Hits 943 965 +22 Misses 153 153 Partials 10 10 ``` | [Flag](https://app.codecov.io/gh/chanzuckerberg/cellxgene-ontology-guide/pull/212/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=chanzuckerberg) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/chanzuckerberg/cellxgene-ontology-guide/pull/212/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=chanzuckerberg) | `85.54% <100.00%> (+0.28%)` | :arrow_up: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=chanzuckerberg#carryforward-flags-in-the-pull-request-comment) to find out more.

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