Add metadata suport for consul

[eduosi]

What is the purpose of the change

The metadata center does not complete support for consul and cannot subscribe to services. apache/dubbo#14870

Brief changelog

Improved Metadata Center support for consul.

Verifying this change

Yes

Follow this checklist to help us incorporate your contribution quickly and easily:

• Make sure there is a GITHUB_issue field for the change (usually before
  you start working on it). Trivial changes like typos do not require a GITHUB issue. Your pull request should address
  just this issue, without pulling in other changes - one PR resolves one issue.
• Format the pull request title like [Dubbo-XXX] Fix UnknownException when host config not exist #XXX. Each commit
  in the pull request should have a meaningful subject line and body.
• Write a pull request description that is detailed enough to understand what the pull request does, how, and why.
• Write necessary unit-test to verify your logic correction, more mock a little better when cross module dependency
  exist. If the new feature or significant change is committed, please remember to add sample
  in dubbo samples project.
• Run mvn clean install -DskipTests=false & mvn clean test-compile failsafe:integration-test to make sure
  unit-test and integration-test pass.
• If this contribution is large, please follow
  the Software Donation Guide.