Stop depending on source location hierarchy for verification

[keyboardDrummer]

What was changed?

• Stop depending on source location hierarchy for verification. There are several IDE related features that still depend on source location hierarchy, but that is mostly important when working with Dafny source code, so that's OK for downstream tools that compile to Dafny

How has this been tested?

• Had to update some existing tests since now the location based API requires targeting the name of a symbol, not just any location inside the symbol.

By submitting this pull request, I confirm that my contribution is made under the terms of the MIT license.

[robin-aws]

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