feat: add basic implementation for bolton43 option to ept

[VeraChristina]

Description

Add bolton43 option for ept computation, following equation (43) from Bolton 1980.
The current implementation only adds this option for the computation of equivalent potential temperature (ept_from_dewpoint and ept_from_specific_humidity) not for other related thermodynamic methods. Support for those could be added in a later PR.

Contributor Declaration

By opening this pull request, I affirm the following:

• All authors agree to the Contributor License Agreement.
• The code follows the project's coding standards.
• I have performed self-review and added comments where needed.
• I have added or updated tests to verify that my changes are effective and functional.
• I have run all existing tests and confirmed they pass.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.24%. Comparing base (688d7f2) to head (f11d691).

Additional details and impacted files

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  Coverage    99.24%   99.24%           
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  Files           27       27           
  Lines         2384     2384           
  Branches        44       44           
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  Hits          2366     2366           
  Misses           9        9           
  Partials         9        9           

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