Switches coveralls to coverage, since we have not used coveralls since
2018.
Additionally, we've added gcov tooling support as both an automatic
target, and manual instructions.

The rest of the diff is changing coveralls into coverage

As a first step for switching from TCMalloc to JEMalloc as the custom
memory allocator, this commit removes every instance of the flag
TCMALLOC_LIBRARIES_LINKTIME in all the CMakeList.txt files. This flag
was never used by the code, so this commit is invisible project-wise.

The format of the sample environment xml file has been extended to support
loading a .stl file for each environment component. An example spec file
has been created in ISIS/Pearl.xml. This can be used when running the
Algorithm SetSample
Various SampleEnvironmentXXX units have been moved out the Geometry package
into the DataHandling package to facilitate this because they needed to
access the STL loading code in DataHandling
SetSample contains some features for overriding the sample geometry if the
geometry is a CSGObject. This has been sidestepped for mesh geometries.
The methods setId and setMaterial have been moved up to IObject because
it's useful to have them applicable to all objects (CSG, mesh)
Some of the repeated code in SetSample, LoadSampleEnvironment (and now
SampleEnvironmentSpecParser) has been centralised in a new class LoadStlFactory
Also changed container logic so that if there's only one container specified
in the env spec file you don't need to specify it in SetSample
Centralise code relating to scaling mesh vertices and handling of units
into the LoadShape class and rename it MeshFileIO now that SaveStl is also
descended from this class
Move repeated code to choose Ascii or binary STL reader into a factory class

Dependencies now go into Frameworks as seems to be done for
other application bundles. This should bring us close to
be able to sign the app bundle

Use macOS over OSX to refer to system.
Remove old OSX version workarounds
Refs #26261

Co-Authored-By: alicerussell1 <46603316+alicerussell1@users.noreply.github.com>

The generation is now handled by free functions in Geometry::RandomPoint.

Re #24636

re #23145

re #23145

re #23145

re #23145

As far as GeometryHandler is concerned, MeshObject and MeshObject2D can
be treated the same.

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Merge done to enable documentation be be fixed, because of removal of
alias directive and addition of related algorithms directive.

Signed-off-by: Karl Palmen <karl.palmen@stfc.ac.uk>

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