comply with EIP-5593

[kdenhartog]

This limits the places where the provider object will be injected to comply with W3C secure contexts which can be found here https://www.w3.org/TR/secure-contexts/

Explanation

This limits the places where the provider object will be injected to comply with W3C secure contexts which can be found here https://www.w3.org/TR/secure-contexts/

More Information

See EIP-5593

Before

the provider object was able to be injected in non-secure contexts and now it's limited to fewer places where it can be injected.

After

Please be aware there is some limitations here that can break things, so please consider this or offer feedback of how we should address this in the ethereum magicians thread.

Manual Testing Steps

See EIP-5593 which defines where it can be used. I'll be authoring a test suite for it soon as well to make it easier to test compliance.

Pre-Merge Checklist

• PR template is filled out
• IF this PR fixes a bug, a test that would have caught the bug has been added
• PR is linked to the appropriate GitHub issue
• PR has been added to the appropriate release Milestone

+ If there are functional changes:

• Manual testing complete & passed
• "Extension QA Board" label has been applied