feat: add PREPEND_LOCALE_PATHS configuration setting to Maple

[keithgg]

edx-platform currently supports COMPREHENSIVE_THEME_LOCALE_PATHS setting, which appends paths to the end of LOCALE_PATHS, but there's currently no way to add additional paths to the start of the list to override the default translations.

In this PR, we added the PREPEND_LOCALE_PATHS configuration setting to achieve this.

Note: This is a cherry-picked commit from the PR: #6677

Configuration Pull Request

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Thanks for the pull request, @keithgg! I've created OSPR-6688 to keep track of it in JIRA, where we prioritize reviews. Please note that it may take us up to several weeks or months to complete a review and merge your PR.

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[pkulkark]

LGTM 👍

[keithgg]

@natabene can someone take a look at this PR as well? My apologies for not pinging earlier.

[natabene]

@keithgg Thanks for letting me know. I will line this up for our review.

[nadeemshahzad]

Hey, @keithgg Thanks for backporting the change in the maple. Can you please rebase your branch?

[keithgg]

Hi @nadeemshahzad, thanks for reviewing. I've rebased.

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