Optimize reference discovery parsing

MR overview https://www.youtube.com/watch?v=XCqiMeeoaYQ

Relevant docs, blogs:

• https://go.dev/blog/slices-intro
• https://go.dev/blog/slices
• https://go.dev/blog/pprof
• https://dave.cheney.net/2013/06/30/how-to-write-benchmarks-in-go