☂ Make C-APIs require C++ compiler

[zwoop]

• Change compiler options of all plugins to be c++, optionally rename .c files to .cc ?
• Assure that when including ts/ts.h, we have a C++ compiler
• Eliminate all tests around being in C compiler state
• Fix tsxs to only work with C++ compilers (fail / error if not)
• Consider what "internal" C++ include files can and should be made public includes
• Cleanup the mess with libswoc in two places
• Break out APIs into its own .so
• Namespaces

The goal is not to break the C-API, but to enforce that a C++ compiler is always used going forward.

[zwoop]

Blocks: #5457

[zwoop]

Deferring this to v10.0.0, since there's little interest, and some opposition. The C-APIs will stay C for the next 2-3 years.

[github-actions]

This issue has been automatically marked as stale because it has not had recent activity. Marking it stale to flag it for further consideration by the community.