Select all databases to migrate by default and Import feedback.

[stuti149]

This PR has two changes:

1. Select all databases by default to migrate on Assessment results page. (changes inassessmentDetailsPage.tsfile)

2. Import feedback by Abhishek - (changes in importAssessmentDialog.ts file)
   a. Change Import heading.
   b. Select MI as default on import page and don't show no target selection page.

[coveralls]

Pull Request Test Coverage Report for Build 6954489630

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage decreased (-0.002%) to 41.569%

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Files with Coverage Reduction	New Missed Lines	%
extensions/notebook/src/book/bookTreeView.ts	1	36.91%

Totals
Change from base Build 6953970717:	-0.002%
Covered Lines:	30791
Relevant Lines:	69372

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💛 - Coveralls