client: measure CPU time of VBox apps correctly

[davidpanderson]

We were checking for VBoxSVC.exe and, if a VBox app is running, counting its CPU time as BOINC-related.
Should be 'VBoxHeadless.exe' on Win.
May be different on Mac/Linux, so use 'vbox', case-insensitive

[computezrmle]

Not all vbox processes are necessarily BOINC related.
Imagine VMs running in the background to provide special services like

• E-mail
• DB
• a compile service

Thus, only those processes should be included that are in the BOINC process tree.
In addition there may be more than 1 BOINC client running on a computer and each of them has its own process tree.

[AenBleidd]

@davidpanderson, please fix Windows build

[davidpanderson]

The VBoxHeadless.exe processes are in the VBoxSVC.exe process tree, the BOINC client tree.
I don't know how to identify them as BOINC jobs.

In any case: the only thing this affects is the "suspend if non-BOINC CPU usage exceeds X" pref,
whose purpose is to ensure fast interactive response, e.g. if the user does a compile.
It's critical that we not suspend BOINC because of its own computation.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 2 lines in your changes missing coverage. Please review.

Project coverage is 10.75%. Comparing base (f27cc8e) to head (b9eb3c6).
Report is 86 commits behind head on master.

Files with missing lines	Patch %	Lines
lib/procinfo.cpp	0.00%	2 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #5867      +/-   ##
============================================
+ Coverage     10.51%   10.75%   +0.23%     
  Complexity     1068     1068              
============================================
  Files           280      280              
  Lines         36021    36552     +531     
  Branches       8441     8471      +30     
============================================
+ Hits           3789     3930     +141     
- Misses        31843    32233     +390     
  Partials        389      389              

Files with missing lines	Coverage Δ
lib/procinfo.h	0.00% <ø> (ø)
lib/procinfo.cpp	0.00% <0.00%> (ø)

... and 102 files with indirect coverage changes

[AenBleidd]

@computezrmle, could this be later better handled with the new functionality introduced in #5870?