Miscelleaneous bug fixes & improvements

[AnErrupTion]

• Fixed usage of deprecated cpuid option in Bochs (replaced with cpu option)
• Static options are now parsed first rather than the runtime options first
• Added a compiler exception when the module for an extern method isn't found (e.g. when compiling for the wrong platform)
• Made the instruction stage combo box reset every time a new file is opened
• Made the fonts in the large text boxes monospace in the Avalonia Explorer tool
• Added Mosa.UnitTests.TinyCoreLib inside the UnitTests solution folder (forgot to do that in the last PR, oops)
• Fixed wrong constant value for null objects in the Sparse Conditional Constant Propagation optimisation

[charsleysa]

LGTM