Reduce duplication of build scans guides

We currently have quite obvious duplication between https://guides.gradle.org/creating-build-scans/ and https://scans.gradle.com/get-started.

@etiennestuder @ldaley Do you think it would be a good idea to redirect https://scans.gradle.com/get-started to https://guides.gradle.org/creating-build-scans/? @kousen could implement any changes that may be needed in the latter.

Compare the two linked pages, https://guides.gradle.org/creating-build-scans/ and https://scans.gradle.com/get-started/, to document the duplication and determine whether the proposed redirect is still wanted. Review the changes needed on the guides page, then verify the redirect destination and that the resulting documentation covers the existing get-started content.

Written by the indexing model from the issue text.