fix(http/file_server): dealing with dir listing view that contain system files

[ayame113]

close #3141

When I launch a file server in the Windows root directory and access http://localhost:4507/, I get a 500 Internal Server Error.
It seems that the following error occurs internally. These are Windows system files that reject Deno.stat calls.

The process cannot access the file because it is being used by another process. (os error 32): stat 'C:\/DumpStack.log.tmp'
The process cannot access the file because it is being used by another process. (os error 32): stat 'C:\/hiberfil.sys'
The process cannot access the file because it is being used by another process. (os error 32): stat 'C:\/pagefile.sys'
Access is Denied. (os error 5): stat 'C:\/PerfLogs'
Access is Denied. (os error 5): stat 'C:\/Recovery'
The process cannot access the file because it is being used by another process. (os error 32): stat 'C:\/swapfile.sys'
Access is Denied. (os error 5): stat 'C:\/System Volume Information'

This PR adds a try-catch around the Deno.stat call so that directory listing views are generated even for directories containing system files.
After this PR, the display of the root directory page looks like this:

[ayame113]

Adding this line will make debugging easier as error messages will be displayed instead of discarded. It was a minor change so I've included it in this PR.

[kt3k]

Not directly related to this change, but "[non-error thrown]" message doesn't look useful. How about just printing error itself?

[ayame113]

Makes sense. It has changed! (d8137cb)

[kt3k]

LGTM