[CASESession] Factoring Out Sigma2 and Sigma3 Parsing Functions for Improved Testability (project-chip#36941)

* - Creating an overload of DecodeMRPParametersIfPresent that takes SessionParameters as an outparam and does not touch PairingSession class member mRemoteSessionParameters
- a utility SetRemoteSessionParameters to be able to set PairingSession class member mRemoteSessionParameters

* Making ParseSigma1 static and not dependent on class state

* factoring out ParseSigma2

* factor out Parser for decrypted Sigma2

* various cleanup

* factor out ParseSigma2Resume

* Adding Unit Tests

* More Various Cleanup

* Factor out ParseSigma3 and ParseSigma3TBEData

* Unit Tests for ParseSigma3 and ParseSigma3TBEData

* Code Cleanup

* Integrating Comments and Adding comments

* Increase Coverage of TestSigma1Parsing

* Integrating Comments

* Integrating comments

Author: Alami-Amine