feat(sat): telemetry support and startup / shutdown cleanup

[javorszky]

Closes #54

• Reworked the startup / shutdown so there's a clearer place where everything happens rather than being distributed into different parts of the codebase.
• Added tracing support that's configurable much the same way as Atmo is
• Reworked tests to support the new functionality
• Added a new Options to be behind Config for things that are statically set rather than dynamically figured out

[cohix]

Added a few comments. One thing I'm not seeing is the tracer being used anywhere. I would have expected it to be mounted on Sat's Vektor router and also some manual tracing being added to handleFnResult in meshed.go. Is that coming in another PR?

[javorszky]

@cohix I've added tracing code to both the vektor end of things, and the grav end of things.

The code assumes that the handler func in sat/handler.go file is the first and only entry point for http messages (code / routing seems to suggest that)

And it also assumes that the handleFnResult func in sat/meshed.go files it the first and only entry point for messages arriving via grav, and that the two send* funcs are only called from the handleFnResult func.

[cohix]

After 58 is fixed up and merged, this is good to go! Well done.