refactor: cleanup namespaces and unneeded includes

[braindigitalis]

Removes redundant includes from the cpp files.
Also as we agreed we didnt need to flag namespace closing with a comment (all good ides can do this and we rarely go more than one namespace deep, the dpp namespace) i have gone through and removed them.

Code change checklist

• I have ensured that all methods and functions are fully documented using doxygen style comments.
• My code follows the coding style guide.
• I tested that my change works before raising the PR.
• I have ensured that I did not break any existing API calls.
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[Neko-Life]

lgtm. Need rebase, probably <cstdint> in dev can be removed too