Update governance to establish steering committee and increase contributor diversity

[jbw976]

Description of your changes

This PR updates the Crossplane project governance to meet the following goals:

• Increase diversity of maintainers, enable more organizations to collaborate and have ownership
• Allow varying permissions and access across multiple repos and multiple maintainers
• Improve change velocity by expanding number of maintainers that can approve and merge pull requests
• Formalize responsibilities at the top level for the purpose of project stewardship, adoption, growth and health of the community, and strategic direction

This governance update includes the following high level changes:

• Institute a steering committee at the organization level responsible for overall project direction and health, as well as conflict resolution
• Define a bootstrapping and election process for filling the steering committee with members
• Enable each repository to define its own maintainer team and membership to increase the efficiency of accepting new code changes and instill a sense of ownership more broadly
• Allow new repositories to be bootstrapped with maintainers that do not meet the minimum time length requirements
• Empower each maintainer team to perform conflict resolution and voting for issues within their scope

Approval

As per the existing Crossplane governance, this update requires the existing maintainer team to have at least a 2/3 approval in order to ratify and merge.

Checklist

I have:

• Run make reviewable to ensure this PR is ready for review.
• Ensured this PR contains a neat, self documenting set of commits.
• Updated any relevant documentation and examples.
• Reported all new error conditions into the log or as an event, as
  appropriate.

For more about what we believe makes a pull request complete, see our
definition of done.

[skip ci]

[jbw976]

FYI, I plan to get current maintainer approval and merge this PR on Tues May 26th

[bassam]

We will announce the 2 additional steering committee seats in the next few weeks.

[negz]

Thanks for working on this @jbw976! I'm excited to increase the amount and diversity of folks contributing to Crossplane.