[tools] Add callstats.html to analize --runtime-call-stats output

callstats.html in combination with callstats.py can be used to get an in-depth
view on where we spend time in v8. Furthermore, with callstats.html we can
compare different versions of v8/chrome and see where and how performnce
evolved.

Drive-by-fix: add missing copyrights header to ic-explorer.html and format
ic-explorer.html

BUG=

Review-Url: https://codereview.chromium.org/1947413004
Cr-Commit-Position: refs/heads/master@{#36080}