Handle "info symbol" in Rust language mode

When I changed the Rust parser to handle 128-bit ints, this
inadvertently broke some other gdb commands.  For example, "info
symbol 0xffffffffffffffff" now fails, because the resulting value is
128 bits, but this is rejected by extract_integer.

This patch fixes the problem by changing extract_integer to allow
over-long integers as long as the high bytes are either 0, or (for
signed types) 0xff.

Regression tested on x86-64 Fedora 38.

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=31565


Approved-By: Andrew Burgess <aburgess@redhat.com>