gh-101100: Fix sphinx warnings around I/O

Resolves 7 warnings.

Generally: "file object" -> IOBase; "binary"/`byte` read/write -> BufferedIOBase, "text"/`str` read/write -> TextIOBase

Specific cases:

 - `EOFError` is for `input` builtin function which reads a `str`, so `TextIOBase`
 - `os.read` and `os.write` speak bytes but the sentence is about `sys.stdin` and `sys.stdout` which are `TextIOBase`; use the function that gets called by `sys.stdout.write`.
 - `os.exec`: `flush` is talking about files generally, so `IOBase`
 - `email.parser` is talking about binary files / `bytes` so `BufferedIOBase`

Author: cmaloney

Doc/library/email.parser.rst

@@ -155,7 +155,7 @@ message body, instead setting the payload to the raw body.
 
       Read all the data from the binary file-like object *fp*, parse the
       resulting bytes, and return the message object.  *fp* must support
-      both the :meth:`~io.IOBase.readline` and the :meth:`~io.IOBase.read`
+      both the :meth:`~io.IOBase.readline` and the :meth:`~io.BufferedIOBase.read`
       methods.
 
       The bytes contained in *fp* must be formatted as a block of :rfc:`5322`

Doc/library/exceptions.rst

@@ -221,7 +221,7 @@ The following exceptions are the exceptions that are usually raised.
 .. exception:: EOFError
 
    Raised when the :func:`input` function hits an end-of-file condition (EOF)
-   without reading any data. (Note: the :meth:`!io.IOBase.read` and
+   without reading any data. (Note: the :meth:`io.TextIOBase.read` and
    :meth:`io.IOBase.readline` methods return an empty string when they hit EOF.)
 
 

Doc/library/os.rst

@@ -1294,8 +1294,8 @@ as internal buffering of data.
 
       This function is intended for low-level I/O.  For normal usage, use the
       built-in function :func:`open`, which returns a :term:`file object` with
-      :meth:`~file.read` and :meth:`~file.write` methods (and many more).  To
-      wrap a file descriptor in a file object, use :func:`fdopen`.
+      :meth:`~io.BufferedIOBase.read` and :meth:`~io.BufferedIOBase.write` methods (and many
+      more).  To wrap a file descriptor in a file object, use :func:`fdopen`.
 
    .. versionchanged:: 3.3
       Added the *dir_fd* parameter.
@@ -1660,7 +1660,7 @@ or `the MSDN <https://msdn.microsoft.com/en-us/library/z0kc8e3z.aspx>`_ on Windo
       descriptor as returned by :func:`os.open` or :func:`pipe`.  To read a
       "file object" returned by the built-in function :func:`open` or by
       :func:`popen` or :func:`fdopen`, or :data:`sys.stdin`, use its
-      :meth:`~file.read` or :meth:`~file.readline` methods.
+      :meth:`~io.TextIOBase.read` or :meth:`~io.IOBase.readline` methods.
 
    .. versionchanged:: 3.5
       If the system call is interrupted and the signal handler does not raise an
@@ -1895,7 +1895,7 @@ or `the MSDN <https://msdn.microsoft.com/en-us/library/z0kc8e3z.aspx>`_ on Windo
       descriptor as returned by :func:`os.open` or :func:`pipe`.  To write a "file
       object" returned by the built-in function :func:`open` or by :func:`popen` or
       :func:`fdopen`, or :data:`sys.stdout` or :data:`sys.stderr`, use its
-      :meth:`~file.write` method.
+      :meth:`~io.TextIOBase.write` method.
 
    .. versionchanged:: 3.5
       If the system call is interrupted and the signal handler does not raise an
@@ -4341,7 +4341,7 @@ to be ignored.
    The current process is replaced immediately. Open file objects and
    descriptors are not flushed, so if there may be data buffered
    on these open files, you should flush them using
-   :func:`sys.stdout.flush` or :func:`os.fsync` before calling an
+   :func:`~io.IOBase.flush` or :func:`os.fsync` before calling an
    :func:`exec\* <execl>` function.
 
    The "l" and "v" variants of the :func:`exec\* <execl>` functions differ in how