[2.x] Simplify and normalize public navigation APIs

[emmadesilva]

Targets #1568 as I when writing the docs realized that having two NavigationItem constructors with differing syntaxes and internal logic adds a ton of complexity for no real reason. This PR protects the constructor to force a single unified API through the static create method. unifies the constructor signatures and logic to provide the exact same results regardless of the syntax used.

It also changes navigation groups to use collections instead of an array for the internal state to match the navigation group system.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.97%. Comparing base (f7ae4e1) to head (6042642).

❗ Current head 6042642 differs from pull request most recent head 89c4890. Consider uploading reports for the commit 89c4890 to get more accurate results

Additional details and impacted files

@@                         Coverage Diff                         @@
##             improved-navigation-internals    #1642      +/-   ##
===================================================================
- Coverage                            99.97%   99.97%   -0.01%     
+ Complexity                            1778     1775       -3     
===================================================================
  Files                                  184      184              
  Lines                                 4799     4791       -8     
===================================================================
- Hits                                  4798     4790       -8     
  Misses                                   1        1              

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[emmadesilva]

Consider reopening #1630 but rebased to target this branch