[2.7] bpo-32186: Release the GIL during fstat and lseek calls (#4651)

In fileio, there were 3 fstat() calls and one lseek() call that did not
release the GIL during the call. This can cause all threads to hang for
unlimited time when using io.FileIO with inaccessible NFS server.

Same issue seen in fileio exists also in fileobject, fixed in the same
way.
3 files changed