chore: added extra variables owlbot kokoro configs

[daniel-sanche]

This PR adds extra labels to the kokoro tests to make filtering easier for our test dashboards. It adds the following labels:

type: observability product: logging language: node

[generated-files-bot[bot]]

Warning: This pull request is touching the following templated files:

• .kokoro/common.cfg - .kokoro files are templated and should be updated in synthtool
• .kokoro/common_env_vars.cfg - .kokoro files are templated and should be updated in synthtool
• .kokoro/continuous/node12/common.cfg - .kokoro files are templated and should be updated in synthtool
• .kokoro/environment/common.cfg - .kokoro files are templated and should be updated in synthtool
• .kokoro/release/common.cfg - .kokoro files are templated and should be updated in synthtool