flag error in status bar and added a reveal-terminal button in TestExplorer

[connectdotz]

As part of the autoRevealOutput change (#976), this PR added:

• change the status bar item background color for execution errors and warnings, so the critical error will not be completely invisible even when the test output is hidden.
• added the ability to manually open the test output for any workspace from the TestExplorer's context menu.
• fixed a dead link

resolve #978 resolve #973

[coveralls]

Pull Request Test Coverage Report for Build 3879508853

• 78 of 79 (98.73%) changed or added relevant lines in 7 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.3%) to 97.778%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/StatusBar.ts	43	44	97.73%
<!--	Total:	78	79	98.73%	-->

Totals
Change from base Build 3878595132:	0.3%
Covered Lines:	3373
Relevant Lines:	3396

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💛 - Coveralls