Inexorabletash/encoding api

[inexorabletash]

Test for the Encoding Standard's API (TextEncoder/TextDecoder), ported from Chromium/Blink's layout tests.

[hoppipolla-critic-bot]

Critic review: https://critic.hoppipolla.co.uk/r/3713

This is an external review system which you may optionally use for the code review of your pull request.

In order to help critic track your changes, please do not make in-place history rewrites (e.g. via git rebase -i or git commit --amend) when updating this pull request.

[Ms2ger]

@inexorabletash: something weird seems to have happened to the history here; could you try to squash everything into one simple commit?

[inexorabletash]

@Ms2ger: Ugh, sorry - thought I had squashed.

Take a peek now? I'm not sure if I need to do more on the critic side of things.

[inexorabletash]

Per the "...to help critic track your changes..." I may need to drop/resubmit a request. LMK.

[hillbrad]

Critic is very confused by this, showing thousands of lines needing review. Is it possible to drop/resubmit this with just the relevant changes, please?