Add BreakingChange-Approved-Security label and update automation to recognize it

[mikekistler]

The Breaking Change Board would like to add one more label to signal approval of a breaking change, BreakingChange-Approved-Security. This label will be used when the justification for approval is to address a security vulnerability.

PR checks will need to be updated to recognize this new label and unblock merge of a PR flagged for breaking change review when the new label is applied.

[mikeharder]

Fix should be similar to the addition of Versioning-Approved-Retired:

https://dev.azure.com/devdiv/DevDiv/_git/openapi-alps/pullrequest/579729