cmd/trace: beautify goroutine page
cmd/trace: beautify goroutine page

- Summary: also includes links to pprof data.
- Sortable table: sorting is done on server-side. The intention is
  that later, I want to add pagination feature and limit the page
  size the browser has to handle.
- Stacked horizontal bar graph to present total time breakdown.
- Human-friendly time representation.
- No dependency on external fancy javascript libraries to allow
  it to function without an internet connection.

Change-Id: I91e5c26746e59ad0329dfb61e096e11f768c7b73
Reviewed-on: https://go-review.googlesource.com/102156
Run-TryBot: Hyang-Ah Hana Kim <d7e82c3c07f92613bcbf9a1e88f6b96c13caa3b0@gmail.com>
TryBot-Result: Gobot Gobot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Andrew Bonventre <682ad9f487f614f19e8b7cc5d340bdc8e1c1b128@golang.org>
Reviewed-by: Heschi Kreinick <e89ab2b172855aa0ad01c40c4d8a3535a61ac68a@google.com>

josharian/go,akutz/go,CAFxX/go,cloudflare/go,cloudflare/go,CAFxX/go,josharian/go,josharian/go,josharian/go,cloudflare/go,nawawi/go,nawawi/go,golang/go,CAFxX/go,nawawi/go,nawawi/go,nawawi/go,golang/go,Cofyc/go,akutz/go,golang/go,Cofyc/go,josharian/go,akutz/go,CAFxX/go,Cofyc/go,Cofyc/go,nawawi/go,akutz/go,golang/go,akutz/go,nawawi/go,josharian/go,akutz/go,CAFxX/go,josharian/go,nawawi/go,cloudflare/go,golang/go,akutz/go,Cofyc/go,Cofyc/go,golang/go,Cofyc/go,CAFxX/go,cloudflare/go,Cofyc/go,josharian/go,CAFxX/go,golang/go,cloudflare/go,cloudflare/go,CAFxX/go,golang/go,akutz/go,cloudflare/go