GeezerVison

When a binary IOBase subclass provides peek() and read() returns fewer bytes than requested, readline(size) calculates subsequent reads against the original limit instead of the number of bytes still allowed. It can consume and return more than size bytes, leaving less data for the next read. Apply the remaining limit in both the C and pure-Python implementations.

Backport to 3.15 and 3.14. Both branches use a bytearray instead of PyBytesWriter; the test lives in Lib/test/test_io.py on 3.14.

• Issue: Fix minor safety issues #159739