promtool: Speed up checking for duplicate rules

[zecke]

Running promtool check config on large rule files is rather slow. Improve this by adding a testcase, benchmark and changing the algorithm used to find duplicates.

Before:
goos: darwin
goarch: amd64
pkg: github.com/prometheus/prometheus/cmd/promtool
cpu: VirtualApple @ 2.50GHz
BenchmarkCheckDuplicates-8   	       1	9543373875 ns/op

After:
goos: darwin
goarch: amd64
pkg: github.com/prometheus/prometheus/cmd/promtool
cpu: VirtualApple @ 2.50GHz
BenchmarkCheckDuplicates-8   	     187	   6313867 ns/op

[dgl]

@zecke thanks for this, looks good, but there's something strange with CircleCI build, could you merge main into this?

[zecke]

@zecke thanks for this, looks good, but there's something strange with CircleCI build, could you merge main into this?

I lowered the parallelism in circle-ci but now tests fail in code not touched and in go mod sanity checking. I am not sure whether this is related to my changes at all. Needless to say that building locally works.

[roidelapluie]

please revert your circleci changes. it is because you probably also have a circleci account.

[roidelapluie]

the last test failure was done with a run with SSH, so it might have been tampered somehow.

[zecke]

please revert your circleci changes. it is because you probably also have a circleci account.

Reverted. How can we proceed? How can I not associate this with my account? Okay. I was able to unfollow the project which makes the build work/pass. PTAL now.

[dgl]

Going to merge from my account as CircleCI seems unhappy with @zecke's account.

(Per previous comments the tests did succeed, but it didn't post the status to github, so the required check wouldn't let me merge.)

[dgl]

Thank you @zecke! & sorry for the trouble here, I've asked CircleCI if there's anything we can do better for future contributions.

I've merged your exact branch under #9306.