Fix recovery middleware to render gitea style page.

[lunny]

The recent change to recovery middleware will always output trace log content to web browser when panic. It's a regression.

This PR introduced some new middlewares to chi and will fix that and take them back.

• Introduce new render middleware from https://github.com/unrolled/render.
• Introduce new locale middleware which could get the current language.
• Session middleware has been copied and modified to https://gitea.com/go-chi/session.
• Login user panic page should know user information.
• code.gitea.io/gitea/modules/auth/sso has been refactored so that both macaron and chi could use that.
• Improve the Recovery middleware, now it will try to render a friendly UI at first, if panic again, fallback to original method

[codecov-io]

Codecov Report

Merging #13857 (b793642) into master (126c933) will decrease coverage by 0.09%.
The diff coverage is 26.75%.

@@            Coverage Diff             @@
##           master   #13857      +/-   ##
==========================================
- Coverage   41.97%   41.87%   -0.10%     
==========================================
  Files         735      742       +7     
  Lines       78933    79309     +376     
==========================================
+ Hits        33132    33211      +79     
- Misses      40346    40635     +289     
- Partials     5455     5463       +8     

Impacted Files	Coverage Δ
modules/auth/auth.go	61.53% <ø> (-2.51%)	⬇️
modules/auth/sso/reverseproxy.go	9.52% <0.00%> (ø)
modules/middlewares/cookie.go	0.00% <0.00%> (ø)
modules/middlewares/locale.go	0.00% <0.00%> (ø)
modules/middlewares/redis.go	2.15% <2.15%> (ø)
modules/templates/base.go	28.57% <28.57%> (ø)
routers/routes/recovery.go	29.41% <29.41%> (ø)
modules/middlewares/virtual.go	32.29% <32.29%> (ø)
modules/auth/sso/basic.go	51.06% <50.00%> (ø)
routers/init.go	45.79% <50.00%> (-4.61%)	⬇️
... and 21 more

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[lunny]

@6543 All done.

[lunny]

@techknowlogick Could you review this again?

[6543]

🎉