replace dep with go modules (#16017)

- guide shamelessly stolen from prometheus/prometheus
- updates local interface of oauth exchange
- updates local impl of hclogger
- bump jaeger client version

closes #16088

vendor/github.com/prometheus/procfs/CONTRIBUTING.md

@@ -0,0 +1,18 @@
+# Contributing
+
+Prometheus uses GitHub to manage reviews of pull requests.
+
+* If you have a trivial fix or improvement, go ahead and create a pull request,
+  addressing (with `@...`) the maintainer of this repository (see
+  [MAINTAINERS.md](MAINTAINERS.md)) in the description of the pull request.
+
+* If you plan to do something more involved, first discuss your ideas
+  on our [mailing list](https://groups.google.com/forum/?fromgroups#!forum/prometheus-developers).
+  This will avoid unnecessary work and surely give you and us a good deal
+  of inspiration.
+
+* Relevant coding style guidelines are the [Go Code Review
+  Comments](https://code.google.com/p/go-wiki/wiki/CodeReviewComments)
+  and the _Formatting and style_ section of Peter Bourgon's [Go: Best
+  Practices for Production
+  Environments](http://peter.bourgon.org/go-in-production/#formatting-and-style).