feat(instrumentation-koa): Add support for koa 3

[tlindhardt]

Which problem is this PR solving?

• During the upgrade of our project from v2 to v3 I noticed that the span name was not correct and the attributes were missing. Upon further inspection I found that the instrumentation was being skipped entirely.

Short description of the changes

• Switched to ATTR_HTTP_ROUTE from SEMATTRS_HTTP_ROUTE
• Add support to instrumentation-koa for koa v3
• Updated tests
  • This includes removing a test to validate the generator middleware is skipped as that is no longer supported and mentioned in the upgrade guide

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: tlindhardt / name: Tyson Lindhardt (176af97, 487143e)

[tlindhardt]

I wasn't sure of the release process and if I needed to also change the manifest file or not.

[github-actions]

This package does not have an assigned component owner and is considered unmaintained. As such this package is in feature-freeze and this PR will be closed with 14 days unless a new owner or a sponsor (a member of @open-telemetry/javascript-approvers) for the feature is found. It is the responsibility of the author to find a sponsor for this feature.
Are you familiar with this package? Consider becoming a component owner.

[dyladan]

@seemk @JacksonWeber are either of you interested in becoming component owner here?

[tlindhardt]

I went ahead and applied the requested changes.