Fix account refresh issue + enable extHostTreeView tests

[cheenamalhotra]

Fixes #24994

Noticed an issue with extHostTreeViews (vs), where refresh intends to clear children, but because child nodes are not registered in cached parent node, they don't clear and we face the issue above.

For more details: PR microsoft/vscode#199061 addresses the same in VS Code.

Before:

After:

[coveralls]

Pull Request Test Coverage Report for Build 7013341802

Warning: This coverage report may be inaccurate.

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A quick fix for this PR: rebase it; your next report should be accurate.

• 3 of 7 (42.86%) changed or added relevant lines in 2 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage remained the same at 41.566%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
extensions/azurecore/src/azureResource/tree/connectionDialogTreeProvider.ts	0	2	0.0%
extensions/azurecore/src/azureResource/tree/treeProvider.ts	3	5	60.0%

Files with Coverage Reduction	New Missed Lines	%
extensions/notebook/src/dialog/configurePython/configurePythonWizard.ts	1	46.46%

Totals
Change from base Build 6983798953:	0.0%
Covered Lines:	30792
Relevant Lines:	69378

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💛 - Coveralls

[Charles-Gagnon]

How about a test as well? The VS Code people would probably like that too

[cheenamalhotra]

How about a test as well? The VS Code people would probably like that too

I did attempt that, and noticed I had to expose new APIs or internal objects to test the same. We can reproduce the issue in tests, and see that cache doesn't contain the reference to child nodes, but to expose cache from public API seemed a little too much, so I didn't go for it.

[Charles-Gagnon]

We can reproduce the issue in tests - can you make the tests fail when that happens? Having something that checks to make sure this doesn't regress would be great so we don't have to worry about it going forward.