[2.x] DataCollections improvements

[caendesilva]

See the 1.x tie-in to make the upgrade smoother #1733. Fixes #1712

Main changes:

• Breaking: Renamed class DataCollections to DataCollection
  • Fixes part of [2.x] DataCollections improvements #1712
• JSON collection files are now validated
  • Fixes Should data collections throw if data files are invalid? #1736
• Yaml data files no longer need to start with triple dashes to be parsed by DataCollections
  • Fixes part of [2.x] DataCollections improvements #1712
  • (cherry picked to 1.x via [1.x] DataCollections improvements #1733)
• No longer automatically create the data collections directory
  • Fixes DataCollections methods should not create directories #1735
• Adds a new custom ParseException exception

Also adds increased unit testing for syntax options and fault tolerance

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.95%. Comparing base (d87afde) to head (227db4f).

❗ Current head 227db4f differs from pull request most recent head 0a3a65a

Please upload reports for the commit 0a3a65a to get more accurate results.

Additional details and impacted files

@@            Coverage Diff             @@
##             2.x-dev    #1732   +/-   ##
==========================================
  Coverage      99.95%   99.95%           
- Complexity      1789     1806   +17     
==========================================
  Files            184      185    +1     
  Lines           4757     4786   +29     
==========================================
+ Hits            4755     4784   +29     
  Misses             2        2           

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[caendesilva]

Questioning if we should support --- at all, but they are valid (and recommended) spec so I can't justify the BC break of removing them. Still, only the first Yaml document in a file is valid, anything else will be trimmed, and I don't think it's common enough to try this to warrant an exception here. We do handle it gracefully by using Str::between (originally implemented to simplify logic to trim front matter encased Yaml with dashes both above and under)