Halo add pb test for halo exchange

[TomMelt]

Add periodic boundary test for Halo Exchange

Task List

• Linked an issue above that captures the requirements of this PR
• Defined the tests that specify a complete and functioning change
• Implemented the source code change that satisfies the tests
• Commented all code so that it can be understood without additional context
• No new warnings are generated or they are mentioned below
• The documentation has been updated (or an issue has been created to do so)
• Relevant labels (e.g., enhancement, bug) have been applied to this PR
• This change conforms to the conventions described in the README

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Change Description

• Adds a test for halo exchange with periodic boundaries

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Test Description

HaloExchangePB_test.cpp

HaloExchangePB_test.cpp is based on HaloExchangeCB_test.cpp. It creates test data for all the array types:

• HField
• VertexField
• DGField
• DGVector
• CGVector

They are created in such a way that the value of each cell can be calculated based on its indices. Therefore we can check after exchange that all of the cells have been exchanged successfully.

This would be a good PR for @niravshah241 to take over.