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

[seanm]

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"

[seanm]

@yurivict since you probably know FreeBSD well, maybe you would know how to improve ITK here?