Run gofumpt via go tool in dprint

[jakebailey]

This is a lot slower; go tool is faster than go run from 1.23, but still a lot slower than a plain binary. But, this doesn't require any global installs of gofumpt to run dprint. Given the recommendation is to configure gopls to run gofumpt instead, and dprint does cache things, it seems like this isn't such a bad tradeoff to avoid dprint fmt failing unexpectedly for those using that CLI.