Cannot use or export using Cobertura on CoverageResult

**Describe the bug**
I am able to run and get coverage result using Get-CoverTSql PowerShell wrapper function.
Source has a the public string Cobertura(string packageName = "sql", Action customCoverageUpdater = null) line 315 but the method is not visible when consuming in powershell

**To Reproduce**
Steps to reproduce the behavior:
1. Run $result = Get-CoverTSql "$openCoverSourceFolder\SQLCover.dll" $connectionString $databaseName $runtSQLtTestsCmd
2. Try to run $result.Cobertura()
4. See error
Method invocation failed because [SQLCover.CoverageResult] does not contain a method named 'Cobertura'.
At line:1 char:1
+ $result.Cobertura()
+ ~~~~~~~~~~~~~~~~~~~
+ CategoryInfo : InvalidOperation: (:) [], RuntimeException
+ FullyQualifiedErrorId : MethodNotFound

**Expected behavior**
$result = Get-CoverTSql "$openCoverSourceFolder\SQLCover.dll" $connectionString $databaseName $runtSQLtTestsCmd
$result.Cobertura() | Out-File $path
$result.SaveSourceFiles($reportPath)

@GoEddie

Start at the public Cobertura method on CoverageResult around line 315 and review how SQLCover.dll is consumed by the Get-CoverTSql PowerShell wrapper. Reproduce the $result.Cobertura() call, then verify the method is callable from PowerShell and that its output can be piped to a file as shown.

Written by the indexing model from the issue text.