Sidebar: Refactor page attributes to use withAPIData

[aduth]

Related: #1957, #1974

This pull request seeks to refactor Page Attributes sidebar component to use withAPIData instead of its own internal management of fetch requests.

Testing instructions:

Repeat testing instructions from #1957

[codecov]

Codecov Report

Merging #2522 into master will increase coverage by 0.05%.
The diff coverage is 66.66%.

@@            Coverage Diff             @@
##           master    #2522      +/-   ##
==========================================
+ Coverage    30.2%   30.26%   +0.05%     
==========================================
  Files         174      174              
  Lines        5270     5267       -3     
  Branches      900      899       -1     
==========================================
+ Hits         1592     1594       +2     
+ Misses       3121     3117       -4     
+ Partials      557      556       -1

Impacted Files	Coverage Δ
editor/sidebar/page-attributes/index.js	73.68% <66.66%> (+19.13%)	⬆️

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