Improve error logging during apps build for I18n content

[daynew]

When we run yarn build or yarn start, it will look for i18n JSON files owned by the apps project and parse the content using the MessageFormat library. If the content fails to be parsed, the build is failed and an error is logged. There are two improvements we make to this process in this PR:

• Checks for MessageFormat syntax errors one string at a time so we can produce an error for the exact string which is failing. Currently it will just log something like "Failed to parse string in ar_sa/maze.json" which isn't helpful enough because there are thousands of strings in that file.
• Check all i18n content before producing an error summary. Currently the build process reports only the first error it runs into. Usually when we run into these issues is after we have downloaded thousands of new translations from Crowdin. Usually there are many strings which need to be addressed and it is slow/tedious to rerun the build after each string fix.

Links

• JIRA

Testing story

• Manually tested
  I manually created some errors in our JSON files and this was the output of yarn build

Running "messages:all" (messages) task
Warning: All I18n content issues:
Error: key 'danceFeedbackNeedNewDancer' in localization file i18n/dance/ca_es.json has a format issue: SyntaxError: Expected "," or "}" but "d" found.
Error: key 'fishshort-predicting-init1' in localization file i18n/fish/ar_sa.json has a format issue: SyntaxError: Expected "#", "{", doubled apostrophe, end of input, escaped string, or plain char but "}" found.
Error: key 'cancel' in localization file i18n/fish/bn_bd.json has a format issue: SyntaxError: Expected "," or "}" but "ক" found.
Error: key 'continue' in localization file i18n/fish/fi_fi.json has a format issue: SyntaxError: Expected "," or "}" but "J" found. Use --force to continue.

[annaxuphoto]

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