Fix main frame position

[artem-fedorov]

1. Move JMeter window at the top the stacking order of any other windows. (Before: after start JMeter this window can be located under another window)
2. Show JMeter window relative to default graphics device with relative size to it. (Problem now is if you have 2 monitors JMeter shows main frame with dimension relative to summary screen resolution. For example 2 monitors 1920x1080 are summarized to 3840x1080 and JMeter window width will be 80% from 3840)

[codecov-io]

Codecov Report

Merging #338 into trunk will decrease coverage by <.01%.
The diff coverage is 0%.

@@             Coverage Diff              @@
##              trunk     #338      +/-   ##
============================================
- Coverage     57.91%   57.91%   -0.01%     
+ Complexity    10024    10023       -1     
============================================
  Files          1148     1148              
  Lines         73785    73787       +2     
  Branches       7328     7328              
============================================
- Hits          42735    42731       -4     
- Misses        28573    28579       +6     
  Partials       2477     2477

Impacted Files	Coverage Δ	Complexity Δ
.../jorphan/org/apache/jorphan/gui/ComponentUtil.java	0% <0%> (ø)	0 <0> (ø)	⬇️
src/core/org/apache/jmeter/JMeter.java	39.3% <0%> (-0.12%)	43 <0> (ø)
...mpler/hc/JMeterPoolingClientConnectionManager.java	27.77% <0%> (-3.18%)	10% <0%> (-1%)

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