Drop instrumentation support for Go < 1.19

[MrAlias]

As was pointed out here, we have not supported Go 1.19 ...

[...] for 9 months: #790
That is 8 releases without it being reported.

In our last SIG meeting we reached an agreement that we will drop instrumentation support for Go < 1.19 to clean up the code-base and reduce development burden going forward.

Backwards compatible support can be added back in the future. However, dropping this once we stabilize will be more problematic. Based on this the consensus was to remove this support prior to the stabilization of this project.

• Update our inspect tooling to not generate offsets for Go < 1.19
• Remove context tracking support for Go < 1.17 in our included C libraries
• Update our compatibility documentation