Simplify history state storage

[PaperStrike]

Motivation and Context

Current LazyHistory API is a mess. Rewrite it and the new one looks like this:

In window.history.state:

{
  ...others,
  pjax: 1, // The index of current Pjax state in session storage
}

In window.sessionStorage.getItem('pjax') (parsed):

[
  {"scrollPos": [0,535.2000122070312]},
  {"scrollPos": [0,280.79998779296875]}, // Current Pjax state
  {"scrollPos": [0,106.4000015258789]},
]

LazyHistory lib is used to store scroll position.

How Has This Been Tested?

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Refactor (no bug fix and new feature but improvements)

Checklist:

• My change requires new tests.
• I have added tests to cover my changes.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.