* Expose default database collation through 'sql-database-projects' extension API.
For the purpose of schema conversion we would need to know whether target database is configured as CI or CS. This will be used to produce a warning, if we detect a case-sensitive identifier, but database is configured as CI. In order to support this scenario we need to access `<DefaultCollation/>` property of the project.
This change adds new method to the `ISqlProject` interface that allows to read the value of the project property. There already was similar method for the SQL version/platform (`<DSP/>` property) and while working on the change, I took an opportunity to refactor the way project properties are extracted from the XML. Original code was hardcoded in the `getProjectTargetVersion` and I extracted it into separate `evaluateProjectPropertyValue` helper, that can be used in the future by any getter or access method that is supposed to return a value of the single property. This also allows us to improve the way properties are retrieved from the XML. Today the logic is very rudimentary - we read the first matching XML element with the required name. This is not correct as it does not verify the parent to be `<PropertyGroup/>`, neither it evaluates the `Condition` attributes nor property value itself. I did not invest in this, but added a TODO there explaining that the method may not perform as expected.
After the helper method was added, I updated the existing `getProjectTargetVersion` method to leverage it. The only complication here was the error throwing logic, as it was using custom error message. I preserved that, as there were tests verifying it already. For the new accessor method I did not introduce a special error message and rely on generic one I defined for use within the helper method. Additionally, for the collation we return default value of `SQL_Latin1_General_CP1_CI_AS`, if project does not have the property defined. This is what SSDT for Visual Studio shows in the UI when property is missing and I decided to align with that.
Finally, I added tests for both - original `getProjectTargetVersion` and new collation extraction method to make sure they work as expected. While working on the tests, I've noticed complaints that some rejected promises were not awaited. I added missing `await`s.
