B szymanowski/tgov1 tests dev

[BSzymanowski]

Description

Added tests for TGov1. Hard-coded values included to test the residual from the equations.

Proposed changes

• Function 'TestOutcome residual' added

-generates a bus and Genrou object for reference
-checks the residual hard-coded answers with the results from the Tgov1 equations

Checklist

• All tests pass.
• Code compiles cleanly with flags -Wall -Wpedantic -Wconversion -Wextra.
• The new code follows GridKit™ style guidelines.
• There are unit tests for the new code.
• The new code is documented.
• The feature branch is rebased with respect to the target branch.
• I have updated CHANGELOG.md to reflect the changes in this PR. If this is a minor PR that is part of a larger fix already included in the file, state so.

Further comments

Kindly provide comments so that I may change the code if necessary.