* feat: customizable static assets
This change provides the means to override specific assets from the embedded Go FS with files situated on disk.
We only allow overriding the following files currently:
* favicon.ico
* logo.png
* refactor(server): make logo string a const
* refactor(suites): override favicon and use ntp3 in traefik2 suite
* test(suites): test logo override in traefik2 suite
* test(suites): test asset override fallback in traefik suite
Closes#1630.
