ci: call rtCamp/wp-shared-workflows at @v1

[aryanjasala]

rtCamp/wp-shared-workflows is now tagged v1.0.0, and @v1 moves forward to compatible v1.x releases. This moves the CI caller off the release/v1.0.0 branch, which the shared workflows' own docs say not to pin.

Changes

• .github/workflows/test-measure.yml: wp-ci.yml@release/v1.0.0 becomes wp-ci.yml@v1, and the "pinned during the private pilot" note goes.
• docs/internal/maintenance.md: the dependency table catches up. The Shared CI row now describes @v1, rtcamp/wp-primitives is ^2.0, and the @rtcamp packages use ^ ranges from the npm registry instead of git branches.

@v1's wp-ci.yml takes every input this caller passes (project-type, php-versions, wp-versions, test-php-exclude), plus a new runs-on that defaults to GitHub-hosted ubuntu-latest.

Testing

• actionlint passes on test-measure.yml
• This PR's own CI runs through @v1