Expand on graphs llvm-test-suite tests

[EwanC]

DPC++ runtime testing is done through llvm-test-suite tests, while compilation testing is done in the sycl/test directory

We should have thorough runtime testing to accompany a DPC++ prototype implementation of SYCL_EXT_ONEAPI_GRAPH.

Tests for the record & replay API can already be found in https://github.com/Bensuo/llvm-test-suite however these need to have tests for the explicit API added to them.

[EwanC]

A note that intel/llvm-test-suite has been archieved and we should move our testing to the new intree folder instead - intel#8782

[EwanC]

A note that intel/llvm-test-suite has been archieved and we should move our testing to the new intree folder instead - intel#8782

This is being done preemptively in EwanC#1

Edit: now done in #158

[EwanC]

Closing issue now that #158 is merged, more specific additions to testing can be their own new issue.