maint: Match semantic convention version to SDK semantic conventions

[JamieDanielson]

Which problem is this PR solving?

• it's easy to mismatch semantic convention versions (see notes in feat: return errors from resource.New #59 )

Short description of the changes

• Drop our version of semantic conventions to 1.17 to match those used in the imported otel-go package
• Update the README to clarify versions in use (note old semconv listed because that's in current available release)
• Update releasing notes to remember to adjust README if versions change, and some other cleanup for consistency to other repos
• Add simple unit test for checking semantic convention version against otel-go imported package semantic convention
• Add unit tests for resource detector from core (WithHost) and contrib (lambda) to confirm no schema error

How to verify that this has the expected result

Using a detector on the same version should work. These tests should fail if you change the semantic convention version back to 1.18.0 in the imports.

[vreynolds]

🎉