MainActivity: connection test: block ui when connecting

add editorconfig

MainActivity: connection test: show key in monospace

MainActivity: connection test: show key fingerprints

MainActivity: connection test: fix success message

MainActivity: connection test: print host key

does not store and verify it in SAF yet, but it is a step forward

MainActivity: run connection test on another thread

MainActivity: add a button for testing connection

SFTPDocumentsProvider: set dummy flag

we do not support any of the flags yet, but this should prevent
DocumentsUI with docinfo from crashing

SFTPDocumentsProvider: unify stat filling

SFTPDocumentsProvider: make title url-ish

SFTPDocumentsProvider: append mount path to title

SFTPDocumentsProvider: do not add port to title if canonical

SFTPDocumentsProvider: add summary

SFTPDocumentsProvider: correct connection resetting

SFTPDocumentsProvider: proper error handling

SFTPDocumentsProvider: refactor toasting

reformat code

fix various lints

build: bump sshlib to 2.2.20