fix: get supported languages before fetching codeTemplate (#618)

[zmen]

• get the supported language for current problem when fetchProblemLanguage. If user's default language is not supported, user can select one of them, instead of seeing an error.

• call fse.createFile after "Fetching problem data...". No file will be created if we have error during fetching.

• seems some problems are not correctly ordered by its question id (for example, No.180, No.184), so I change reverse to sort.