Add command line argument to specify screenshot save directory

[nowsprinting]

Screenshot save directory can be also specified by command line arguments -testHelperScreenshotDirectory.

[github-actions]

Code Metrics Report

	master (0ec8626)	#63 (e91482b)	+/-
Coverage	65.3%	66.8%	+1.5%
Code to Test Ratio	1:2.0	1:2.0	+0.1
Test Execution Time	5m6s	3m15s	-1m51s

Details

  |                     | master (0ec8626) | #63 (e91482b) |  +/-   |
  |---------------------|------------------|---------------|--------|
+ | Coverage            |            65.3% |         66.8% |  +1.5% |
  |   Files             |               23 |            24 |     +1 |
  |   Lines             |              524 |           548 |    +24 |
+ |   Covered           |              342 |           366 |    +24 |
+ | Code to Test Ratio  |            1:2.0 |         1:2.0 |   +0.1 |
  |   Code              |              543 |           543 |      0 |
+ |   Test              |             1068 |          1103 |    +35 |
+ | Test Execution Time |             5m6s |         3m15s | -1m51s |

Code coverage of files in pull request scope (100.0% → 100.0%)

Files	Coverage	+/-
Runtime/Attributes/TakeScreenshotAttribute.cs	100.0%	0.0%
RuntimeInternals/CommandLineArgs.cs	100.0%	+100.0%
RuntimeInternals/ScreenshotHelper.cs	100.0%	0.0%

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Reported by octocov