Clean up CreateFile loop in ReadUTF8File

ReadUTF8File in the Settings library tries three times to read the settings file. If the size changes while it is being read, it'll try again.

Right now, the code looks like this (roughly):

while(tries) {
    open
    check permissions
    read in full
    check read size
}

It's expensive to open the file and check the permissions every time. Instead, we could:

open
check permissions
while (tries) {
    reset file pointer
    read in full
    check read size
}

That'll save us closing/reopening the file up to three times.

Locate ReadUTF8File in the Settings library and inspect its current retry loop. Confirm how the file pointer is reset and how permissions and read size are checked; done means the file is opened and permissions are checked once while retries reuse the open file without changing behavior.