[Backport + Bugfix] Move polyfill JavaScript code to be included as a remote script from the head block

[ihor-sviziev]

Description

I investigated issue described in #16568 and found that we have 2 different polyfill implementaions for localStorage and sessionStorage:

1. Added to page html (https://github.com/magento/magento2/blob/2.2-develop/app/code/Magento/Theme/view/frontend/templates/js/polyfill.phtml)
2. As part of jquery.storageapi library - https://github.com/magento/magento2/blob/2.2-develop/lib/web/jquery/jquery.storageapi.min.js

These implementation are fully different. 1st one works good, but 2nd one adds strange behavior - adds separate cookie with ls_ prefix in name for each item that should be stored in localstorage and ss_<some_id>_ for session storage. As result - when customer goes through website - it will add new and new cookies (because of this strange ss_<some_id>_ prefix).

For some reasons sometimes, probably because of race conditions, we're having 2nd implementation used instead of 1st one.

This PR moving 1st implementation into head section (before requirejs), so it will be loaded first for sure.

Also it doing partial backport of #14318 to 2.2-develop branch in order not to add backward incompatible changes.

Fixed Issues (if relevant)

1. local/session storage is mismanaged, particularly when it doesn't exist #16568: local/session storage is mismanaged, particularly when it doesn't exist
2. Unable to send the cookie. Maximum number of cookies would be exceeded #7931: Unable to send the cookie. Maximum number of cookies would be exceeded
3. Incorrect message: Unable to send the cookie. Maximum number of cookies would be exceeded #17195: Unable to send the cookie. Maximum number of cookies would be exceeded

Related Pull Requests

1. Update Cookie Manager library to make max cookie number configurable #10516: Update Cookie Manager library to make max cookie number configurable
2. Update cookie limit to 300 #10961: Update cookie limit to 300

Manual testing scenarios

1. N/A

Contribution checklist

• Pull request has a meaningful description of its purpose
• All commits are accompanied by meaningful commit messages
• All new or changed code is covered with unit/integration tests (if applicable)
• All automated tests passed successfully (all builds on Travis CI are green)

[magento-engcom-team]

Hi @ihor-sviziev. Thank you for your contribution
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[VladimirZaets]

Hi @ihor-sviziev, thank for collaboration. I think we can remove template attribute from the head.polyfill block declaration at all. What do you think?

[ihor-sviziev]

Hi @VladimirZaets,
Good idea.

However we found an issue with current implementation in Safari and Firefox with disabled localstorage support. We're getting an error "Error: Attempted to assign to readonly property.".

After this issue all another JS files (including magento components) just doesn't work.

Related issues (with localstorage polyfills): mortzdk/localStorage#1 https://gist.github.com/orion110217/ef26968000df7290de03a8f774b46b79#gistcomment-2316288

Looks like fix will be much harder than I thought.

PS: We were able to reproduce issue #16568 by disabling localstorage in Firefox and applying this patch.

[ihor-sviziev]

@magento-engcom-team give me 2.2.5 instance

[magento-engcom-team]

Hi @ihor-sviziev. Thank you for your request. I'm working on Magento 2.2.5 instance for you

[magento-engcom-team]

Hi @ihor-sviziev, here is your Magento instance.
Admin access: https://i-17033-2-2-5.engcom.dev.magento.com/admin
Login: admin Password: 123123q
Instance will be terminated in up to 3 hours.

[ihor-sviziev]

I found really good steps to reproduce. Described them in #17195

[ihor-sviziev]

We had long discussion with @VladimirZaets in slack and decided that following changes can't fix the issue.

We found following things:

1. polyfill js doesn't work correctly because window.localStorage is read only. As a workaround we could use another variable name.
2. jquery.storageapi.js library contains a lot of issues and we can't fix them in 2.2 release line as it will be backward incompatible change
3. as jquery.storageapi.js library contains a lot of issue and it's not supporting anymore - it's better to replace this library with another one as part of 2.3 release line

I'm closing this PR as it's not fixing real issue