Simplify and re-order entrypoint HTML document
Simplify and re-order entrypoint HTML document

This patch improves the <head> ordering as discussed in [1], and
applies some further simplifications (such as omitting optional tags)
in line with Google’s HTML Style Guide [2].

[1]: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/2575084/1..5/front_end/entrypoint_template.html#b10
[2]: https://google.github.io/styleguide/htmlcssguide.html

Change-Id: Icda88e0e29591398d35e888c43190f9b3730dbe8
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/2581931
Auto-Submit: Mathias Bynens <17a2cbc4e33156874a9862b0f530521117e66a3d@chromium.org>
Commit-Queue: Jan Scheffler <8abd9e3d93041d096604cb2a1b3070dd7075ba7b@chromium.org>
Reviewed-by: Jan Scheffler <8abd9e3d93041d096604cb2a1b3070dd7075ba7b@chromium.org>

ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend