Add documentation to run unit-test through Intellij

[mikepapadim]

Description

Add entry to documentation to explain the cofiguration for running unit-tests through Intellij.

Backend/s tested

Mark the backends affected by this PR.

• [ ] OpenCL
• [ ] PTX
• [ ] SPIRV

OS tested

Mark the OS where this PR is tested.

• [ ] Linux
• [ ] OSx
• [ ] Windows

Did you check on FPGAs?

If it is applicable, check your changes on FPGAs.

• [ ] Yes
• [ ] No

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