Added button to copy file name in PR files (#35509)

The merge request file viewer has a button for copying the file path,
but it is not always convenient. Often, you only want to copy the file
name, which is currently not possible. This change request adds this
capability.

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Signed-off-by: wxiaoguang <wxiaoguang@gmail.com>
Co-authored-by: a.kiselev <a.kiselev@reglab.ru>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

options/locale/locale_en-US.ini

@@ -109,6 +109,7 @@ copy_path = Copy path
 copy_success = Copied!
 copy_error = Copy failed
 copy_type_unsupported = This file type cannot be copied
+copy_filename = Copy filename
 
 write = Write
 preview = Preview