SqlServerDsc.Common: Rename parameter for Connect-Sql

Details of the scenario you tried and the problem that is occurring

The helper function Connect-SQL should have the parameter SetupCredential renamed to ImpersonateAsCredentials to more clearly indicate that impersonation should be made using SQL Server Database Engine instance credentials.

https://github.com/dsccommunity/SqlServerDsc/blob/25a59632cb82796e1eb998dda734ec6aff7deece/source/Modules/SqlServerDsc.Common/SqlServerDsc.Common.psm1#L486

This will be more relevant with the issue https://github.com/dsccommunity/SqlServerDsc/issues/1579.

Verbose logs showing the problem

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Suggested solution to the issue

See above.

The DSC configuration that is used to reproduce the issue (as detailed as possible)

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SQL Server edition and version the target node is running

Any

SQL Server PowerShell modules present on the target node

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The operating system the target node is running

Any

Version and build of PowerShell the target node is running

n/a

Version of the DSC module that was used

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Start at source/Modules/SqlServerDsc.Common/SqlServerDsc.Common.psm1 around line 486, where Connect-SQL is defined. Search the module for Connect-SQL and SetupCredential usages before making the rename. Done means the parameter and its references consistently use ImpersonateAsCredentials.