[pgAdmin4][Patch]: Fixes #1940 - Handle non-ascii characters in file/folder names

Hi

This patch handles encode/decode issues for files names when following operations are performed such as "create/rename/delete/download/upload" or browsing a file etc.

1) Removed cleanstring() js function which converts ascii characters into its alphabetical characters.

We support ascii characters for file/folder name.

2) Read/Write file in bytes mode(rb/wb) as file need not be always text file.

3) The title of query tab is currently shown encoded, it should be decoded while displaying in tab title.

Please find attached patch and review.

Thanks,

Surinder Kumar