bug(std/_tools): 3rd party import

[timreichen]

Is your feature request related to a problem? Please describe. std/_tools/check_circular_deps.ts is importing a 3rd party mod. std should never import from somewhere other than std. https://github.com/denoland/deno_std/blob/bcc57478422645cba01b9c75d34938e17ba8a383/_tools/check_circular_deps.ts#L3

Describe the solution you'd like Either remove the tool or have deno_graph be included into std.

Describe alternatives you've considered

[nayeemrmn]

I think tools not transitively imported by any public module are exempt. Otherwise imported github actions wouldn't be allowed, the only difference is that these are written in Deno/TS.

[kt3k]

I agree with Nayeem. Scripts under _tools/ should be an exception of that rule