TRUNK-6221: Use LocaleUtils.toLocale() for locales

[trevor-james-nangosha]

Description of what I changed

Use LocaleUtils.toLocale() for locales

Issue I worked on

see https://issues.openmrs.org/browse/TRUNK-6221

Checklist: I completed these to help reviewers :)

• My IDE is configured to follow the code style of this project.

  No? Unsure? -> configure your IDE, format the code and add the changes with git add . && git commit --amend

• I have added tests to cover my changes. (If you refactored
  existing code that was well tested you do not have to add tests)

  No? -> write tests and add them to this commit git add . && git commit --amend

• I ran mvn clean package right before creating this pull request and
  added all formatting changes to my commit.

  No? -> execute above command

• All new and existing tests passed.

  No? -> figure out why and add the fix to your commit. It is your responsibility to make sure your code works.

• My pull request is based on the latest changes of the master branch.

  No? Unsure? -> execute command git pull --rebase upstream master

As per this ticket https://openmrs.atlassian.net/browse/TRUNK-6221, @ibacher suggests that we use
LocaleUtils.toLocale() for the locale handling.
Whereas it can handle both hyphens and underscores, I have seen that it seems to have its own restrictions.

For example, when you pass the following localeSpecification string, en_US_Traditional_WIN it seems to
raise an IllegalArgumentException, especially from the way it handles multi-part variants as seen from the toLocale
and parseLocale functions in this decompiled java class file: (https://github.com/trevor-james-nangosha/files/blob/main/LocaleUtils.class)

For starters, I have decided to use the toLocale function as a default and use our custom logic from before as a fallback.
@ibacher, what do you think about this approach?