CheckFDForStdio determines whether the file at the fd is one written by tini as a stdio rotator.

ListLogsHandler handles the /listlogs/:containerid/..

ListLogsProxyHandler is an HTTP handler that proxies /listlogs/:containerid/..

LogHandler is an HTTP handler that handles the /logs/:containerid/..

LogProxyHandler is an HTTP handler that proxies /logs/:containerid/..

LogViewerProxyHandler is an HTTP handler that proxies all requests to the underlying logviewer, so `/logviewer/:id/foo` will hit `/foo` on the in-container logviewer.