Add tests for asarray method in test_algebra.py

[paskino]

Changes in this pull request

Removed MR tests from the xSTIR/pSTIR/tests directory and moved them to xGadgetron/pGadgetron/tests/test_algebra.py

Testing performed

Related issues

• closes MR specific test in xSTIR/pSTIR/test #1398

Checklist before requesting a review

• I have performed a self-review of my code
• I have added docstrings/doxygen in line with the guidance in the developer guide
• I have implemented unit tests that cover any new or modified functionality
• The code builds and runs on my machine
• CHANGES.md has been updated with any functionality change

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Please tick the following:

• The content of this Pull Request (the Contribution) is intentionally submitted for inclusion in SIRF (the Work) under the terms and conditions of the Apache-2.0 License.