Parameterize strings in CalculateResolution.

Refs #10007.
Rename theta to two theta for clarity.

Refs #10007.
Only fetch instrument once.

Refs #10007.
Make CalculateResolution orientation agnostic.

Refs #10007.
Optimise CalculateResolutionTest.

Refs #10007.
Merge branch 'feature/10007_make_resolution_calculation_more_robust' into develop