Improve media url editing

[shrunyan]

Is your feature request related to a problem? Please describe.
Currently it is unclear that the 'filename property of a media asset controls the url.

Describe the solution you'd like
We should combine the url and filename editing experience into a single field so it clearly communicates changing the filename changes the url. This will need to maintain a button to copy the url.

Describe alternatives you've considered

Additional context

[d88naimi]

@shrunyan How about Edit Filename URL ?

[agalin920]

@shrunyan PR ready for review