Load global storage object in a lazy manner

[cyber-barrista]

Community guidelines:

• I have read and understand the
  contributing guidelines
  and
  code of conduct

This PR contains:

• bugfix
• feature
• refactor
• documentation
• other

Are tests included?

• yes (bugfixes and features will not be merged without tests)
• no

Breaking Changes?

• yes (breaking changes will not be merged unless absolutely necessary)
• no

List any relevant issue numbers:

Description

The global storage object is loaded eagerly, as a result it's evaluated as a side effect whenever the package is loaded, even when just pure functions (e.g. getBucket) are imported/used. It is quite unexpected from user's perspective and makes testing troublesome (e,g. testing the UI part of an extension in non extension environment always fails simply because @extend-chrome/storage is loaded to the bundle)

P.S. There's no system test setup in the repo to test these sort of problems, hence no extra tests added.