fix: do not deadlock sysmon debug logging when covering stdlib - #2260

When COVERAGE_SYSMON_LOG=1, sys.monitoring is replaced by a
LoggingWrapper whose __getattr__ wrapped every attribute access as a
function. Reading constants like COVERAGE_ID then returned a function
instead of the int, so SysMonitor.start() crashed with
"TypeError: '<=' not supported between instances of 'function' and
'int'". Return non-callable attributes unwrapped; only callables are
logged. This is required by the new stdlib-logging test that enables
the debug log (coveragepy#2087).

Signed-off-by: SeaStar Deng <172368758@qq.com>

With COVERAGE_SYSMON_LOG=1, logging a sys.monitoring call inside
SysMonitor.start() (which holds self.lock, added for free-threading in
8b9cecc) triggers PY_START events; the sysmon_py_start callback then
re-enters the same non-reentrant Lock in the same thread and deadlocks.
An RLock lets the callback proceed in the lock-holding thread while
still excluding other threads. Verified with the new
test_sysmon_log_does_not_deadlock_on_stdlib on CPython 3.14.

Signed-off-by: SeaStar Deng <172368758@qq.com>