Use static topology files from datamodel

[sajith]

With this PR:

• All static topology and connection request files will reside in datamodel, and nowhere else.
• In unit tests, pce will use those static files from datamodel.

For reference, topology files were moved to datamodel in atlanticwave-sdx/datamodel#104.

[coveralls]

Pull Request Test Coverage Report for Build 5926089666

• 4 of 4 (100.0%) changed or added relevant lines in 3 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 80.058%

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Totals
Change from base Build 5808566243:	0.0%
Covered Lines:	840
Relevant Lines:	1025

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💛 - Coveralls