Update hashbrown to v0.15.0

[antonok-edm]

#218 describes the situation pretty well; I think a lot of downstream users would appreciate if this could be merged!

I've included a bump to criterion in this PR since it also indirectly depended on hashbrown 0.12.

Closes #218

[kornelski]

Does criterion 0.5 support flags for you?

cargo bench -- --help

works for me with criterion 0.4, but fails to support any CLI flags with criterion 0.5.

[antonok-edm]

@kornelski I've found that they had to add support for it in this PR, but that version has not been released.

In the meantime, adding this to Cargo.toml works:

clap = { version = "*", features = ["help"] }

I've just added that to this PR.

[kornelski]

Oh, if the problem is only limited to the --help flag then that's OK. I thought all flags were broken.