Auto merge of #47063 - kennytm:gate-tools-on-update, r=alexcrichton

Requires tools to test-pass if the corresponding submodule is updated.

Follow up of #46554. Breaking a tool would not stop bors from accepting a merge, but this also means when we intend to *fix* a tool but failed, bors will *still* accept the PR. This behavior is not helpful to the tool maintainers.

This PR attempts to fix this by rejecting the tool-update merge when a tool failed. It recognizes a PR as "tool-updating" when the corresponding submodule is changed, compared with the previous commit.