There is no way to report a close error from `AutoFile` destructor.
Such an error could be serious if the file has been written to because
it may mean the file is now corrupted (same as if write fails).
So, change all users of `AutoFile` that use it to write data to
explicitly close the file and handle a possible error.
Github-Pull: #29307
Rebased-From: dba783538683cfc6af209c640c2d019648493f31
It's useful to be able to seek to a specific position in a file. Allow
AutoFile to seek by using fseek.
It's also useful to be able to get the current position in a file.
Allow AutoFile to tell by using ftell.
New code can call the method without having first to retrieve the raw
FILE* pointer via Get().
Also, move implementation to the cpp file. Can be reviewed with:
--color-moved=dimmed-zebra --color-moved-ws=ignore-all-space
