Run unit tests on 1.18 in addition to 1.17 (#8550)
Run unit tests on 1.18 in addition to 1.17 (#8550)

Run unit tests on 1.18 in addition to 1.17.

Related to https://github.com/open-telemetry/opentelemetry-collector/issues/5032, but for contrib.

In order to merge this PR, an admin for the repo will need to change the branch protection rules for main to require the `build-and-test / unittest (1.18)` and `build-and-test / unittest (1.17)` checks instead of the `unittest` check.
open-telemetry/opentelemetry-collector-contrib,open-telemetry/opentelemetry-collector-contrib