Fix #10160 (see https://help.github.com/en/articles/closing-issues-using-keywords)

Describe changes proposed in this pull request:

• Add structural variant count to detailed studies projection. Extra database query takes around 350ms.

Checks

• The commit log is comprehensible. It follows 7 rules of great commit messages. We can fix this during merge by using a squash+merge if necessary
• Has tests or has a separate issue that describes the types of test that should be created. If no test is included it should explicitly be mentioned in the PR why there is no test.
• Is this PR adding logic based on one or more clinical attributes? If yes, please make sure validation for this attribute is also present in the data validation / data loading layers (in backend repo) and documented in File-Formats Clinical data section!
• Make sure your PR has one of the labels defined in https://github.com/cBioPortal/cbioportal/blob/master/.github/release-drafter.yml

Any screenshots or GIFs?

Example JSON:

{
	"1": {
		"name": "Adenoid Cystic Carcinoma of the Breast (MSK, J Pathol. 2015)",
		"description": "Whole exome sequencing of 12 breast AdCCs.",
		"publicStudy": true,
		...
		"structuralVariantCount": 50,
		...
	}
}

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