Add i18n to server-side messages

[int-y1]

Affected pages:

• /admin/judge/contest/1/change/ > Problems > Rejudge column
• /admin/judge/judge/add/ > Regenerate button
• /admin/judge/submission/ > Rejudge button (and Locked button, if sub is locked)
• /contest/c1/participations/<user> page's title
• Too many running submissions
• Submit to an unviewable problem

[codecov-commenter]

Codecov Report

Merging #1980 (69c6dd5) into master (8faf2bf) will increase coverage by 0.00%.
The diff coverage is 12.50%.

@@           Coverage Diff           @@
##           master    #1980   +/-   ##
=======================================
  Coverage   46.51%   46.51%           
=======================================
  Files         236      236           
  Lines       13085    13086    +1     
=======================================
+ Hits         6086     6087    +1     
  Misses       6999     6999           

Impacted Files	Coverage Δ
judge/admin/contest.py	43.45% <0.00%> (ø)
judge/admin/runtime.py	66.66% <ø> (ø)
judge/views/contests.py	29.23% <0.00%> (ø)
judge/views/problem.py	24.19% <0.00%> (ø)
judge/admin/submission.py	44.89% <33.33%> (+0.28%)	⬆️

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[Xyene]

LGTM, thanks!