Seem unable to detect memory size on FreeBSD; `itkMemoryProbesCollecterBaseTest` test fails

This test fails:

```
Start 711: itkMemoryProbesCollecterBaseTest

711: Test command: /home/builder/external/ITK-bin/bin/ITKCommon2TestDriver "itkMemoryProbesCollecterBaseTest"
711: Working Directory: /home/builder/external/ITK-bin/Modules/Core/Common/test
711: Test timeout computed to be: 1500
711: System: ganesha
711: Processor:
711: Cache: 0
711: Clock: 0
711: Physical CPUs: 12
711: Logical CPUs: 12
711: Virtual Memory: Total: 0 Available: 0
711: Physical Memory: Total: 0 Available: 0
711: OSName: FreeBSD
711: Release: 14.2-RELEASE-p1
711: Version: FreeBSD 14.2-RELEASE-p1 GENERIC
711: Platform: amd64
711: Operating System is 64 bit
711: ITK Version: 6.0.0
711: Name Of Probe (Memory) Iterations Total (kB) Min (kB) Mean (kB) Max (kB) StdDev (kB)
711: Update 1 0 0 0 0 0
711: Total Value 4368520
711: System: ganesha
711: Processor:
711: Cache: 0
711: Clock: 0
711: Physical CPUs: 12
711: Logical CPUs: 12
711: Virtual Memory: Total: 0 Available: 0
711: Physical Memory: Total: 0 Available: 0
711: OSName: FreeBSD
711: Release: 14.2-RELEASE-p1
711: Version: FreeBSD 14.2-RELEASE-p1 GENERIC
711: Platform: amd64
711: Operating System is 64 bit
711: ITK Version: 6.0.0
711: Name Of Probe (Memory) Iterations Total (kB) Min (kB) Mean (kB) Max (kB) StdDev (kB)
711: Update 1 4368520 4368520 4.36852e+06 4368520 0
711: Freeing memory should result in less memory but it is 4438980kB instead of 4368520kB
1/1 Test #711: itkMemoryProbesCollecterBaseTest ...***Failed 2.65 sec

0% tests passed, 1 tests failed out of 1
```

Notice all the zeros.

Also, I noticed that:

` ITK_COMPUTER_MEMORY_SIZE 0`

At first I guessed there was no FreeBSD-specific code for this, but there seems to be:

```
#elif defined(__FreeBSD__) || defined(__OpenBSD__)
public SysResourceMemoryUsageObserver
#else
```

though it comes with comment:

```
* However, SysResourceMemoryUsageObserver is far from being accurate. Other
* way of getting the Memory Usage shall be used.
* For FreeBSD, some alternatives would be to parse the output of
* "sysctl vm.vmtotal" or "sysctl -a | grep -i memory"
```