Don't "unset" open and require after the init context

[mstoykov]

What?

Stop unsetting open and require after init context just do redo some of the work.

This still prevents them being used outside of the init context.

Why?

This was done to prevent them to be used outside of the init context, except that this wasn't enough as you can save them to another variable.

More fixes have been added on top - but in reality there is no need to unset them.

If anything this makes it harder for users to figure out what happens as in the case of require it will tell you that you can't call undefined.

For open this was handled by setting it to a function that just reports it can't be used outside the init context. But this is already the case if it isn't unset and then reset to this function.

So this change makes the whole thing more consistent and doesn't do a bunch of additional and unnecessary operations.

Checklist

• I have performed a self-review of my code.
• I have added tests for my changes.
• I have run linter locally (make lint) and all checks pass.
• I have run tests locally (make tests) and all tests pass.
• I have commented on my code, particularly in hard-to-understand areas.

Related PR(s)/Issue(s)

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 73.58%. Comparing base (55256e6) to head (265a534).
Report is 2 commits behind head on master.

❗ Current head 265a534 differs from pull request most recent head 020624e. Consider uploading reports for the commit 020624e to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3645      +/-   ##
==========================================
+ Coverage   73.56%   73.58%   +0.01%     
==========================================
  Files         277      277              
  Lines       20244    20237       -7     
==========================================
- Hits        14893    14891       -2     
+ Misses       4403     4399       -4     
+ Partials      948      947       -1     

Flag	Coverage Δ
macos	73.49% <100.00%> (?)
ubuntu	73.53% <100.00%> (+0.04%)	⬆️
windows	73.42% <100.00%> (+<0.01%)	⬆️

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