Adopt new Page.getInstallabilityErrors method for PWA checks

[paulirish]

https://chromium-review.googlesource.com/c/chromium/src/+/1560533
https://chromedevtools.github.io/devtools-protocol/tot/Page#method-getInstallabilityErrors

It tests against the real implementation, so we won't have a gap.
https://cs.chromium.org/chromium/src/chrome/browser/installable/installable_logging.cc?l=15-57

This also means we can probably drop manifest parser, manifest-values, etc.
Their offline check is a little different though.

The strings returned are hardcoded english.. but then again so are our current strings. ;)

[connorjclark]

Won't be able to drop manifest-values completely, as many checks aren't handled via the protocol. Example - background color, theme color, icons >= 512px. Which makes sense, the protocol method name suggests it only checks the must haves.

[connorjclark]

see: https://docs.google.com/document/d/1vRjvfLRm7IgqTDf_wza01UJ9nTo-tbaSfY5wlVZAV4c/edit#

[paulirish]

now a dupe of #10515