Task: Opt in SSL Improvements

[LoreleiAurora]

In the core-https meeting we have been discussing how we can improve opt in support for https.
The first stage of this is to introduce constants to force https on various components.

This ticket is the canonical place for this discussion.

So far we are proposing the below constants:
FORCE_SSL #28521
FORCE_SSL_CONTENT #38259
FORCE_SSL_CANONICAL #38260
FORCE_SSL_SCRIPTS #38261

These will be in addition to the existing FORCE_SSL_ADMIN constant.

[iandunn]

Switching from wontfix to maybelater, since that's more accurate.

xref: ​https://make.wordpress.org/core/2019/01/14/follow-up-on-recent-trac-bulk-edit/

[dd32]

Ticket was open with a resolution due to a manual edit, close/re-opening to clear the resolution.

[johnbillion]

Re-closing as a duplicate of #28521. The original plan was to split that ticket out, but it never went anywhere.