feat: simplify destination handling

[skjnldsv]

Instead of using strings, let's require a Folder directly and deduct the data from it

Require a new @nextcloud/files release with nextcloud-libraries/nextcloud-files#731

[codecov]

Codecov Report

Merging #912 (0517a84) into master (1e347c1) will increase coverage by 1.39%.
The diff coverage is 27.27%.

@@            Coverage Diff             @@
##           master     #912      +/-   ##
==========================================
+ Coverage   33.50%   34.89%   +1.39%     
==========================================
  Files           6        6              
  Lines         200      192       -8     
  Branches       31       26       -5     
==========================================
  Hits           67       67              
+ Misses        131      123       -8     
  Partials        2        2              

Files Changed	Coverage Δ
lib/uploader.ts	0.00% <0.00%> (ø)
lib/upload.ts	91.11% <75.00%> (-2.08%)	⬇️

[skjnldsv]

Pushed and fixed tests