Micro optimization in reference to #1852 and #1851.
Use glob.glob(), which internally relies on os.scandir()
in order to list /sys/devices/system/cpu/cpufreq files.
In doing so, we avoid os.path.exists() for each CPU, which
internally uses os.stat().

Signed-off-by: Giampaolo Rodola <g.rodola@gmail.com>

This has always been cause of confusion, e.g. see:
https://github.com/giampaolo/psutil/pull/1727#issuecomment-698934643

Removed the reference to "physical" from dostrings, functions and test.
I still left it in the doc though, as it's more explanatory.

Signed-off-by: Giampaolo Rodola <g.rodola@gmail.com>

Fixes giampaolo/psutil#1708

Add a reusable `psutil_getpagesize()` utility common to all UNIXes.

Related to #1885 (`getpagesize()` is deprecated on recent macOS, POSIX.1-2001 and possibly other UNIXes).

The problem emerged on macOS but `getpagesize()` is also used in FreeBSD, NetBSD, OpenBSD and AIX, so it makes sense to do this in one place only, similarly to Windows which also provide a `psutil_getpagesize()` utility.

Follow cPython's `mmapmodule.c` and `resourcemodule.c` lead and rely on `sysconf(_SC_PAGESIZE)` instead, but leave `getpagesize()` in place as last resort/attempt for systems where it's not deprecated and/or they still legitimately rely on it.

Also provide a python wrapper so we can test the return value of this C function against Python's stdlib modules.

Signed-off-by: Giampaolo Rodola <g.rodola@gmail.com>

"seconds since the epoch" (value returned by `time.time()`) doesn't
depend on the local time zone. It is the same time instance around the
world. It is not in any particular time zone:

```python
import datetime as DT
import zoneinfo

local_time = DT.datetime.fromtimestamp(seconds_since_epoch)    # naive datetime object representing local time
utc_time = DT.datetime.utcfromtimestamp(seconds_since_epoch)  # naive datetime object representing utc time
la_time = DT.datetime.fromtimestamp(seconds_since_epoch, zoneinfo.ZoneInfo("America/Los_Angeles"))   # timezone aware dt
```

Here `local_time`, `utc_time`, `la_time` may correspond to different
clock times but it is exactly the same time instance.