Introduce secret data type

[shamasis]

Password type is essentially a string type. This is also a precursor to allow external hooks into type handling.

• added new password type
• reordered code in type def for cleanliness
• tests
• no breaking change

Edit: We are calling the data type as secret instead of password

[shamasis]

This block is not a change, but merely a code reorder for clean addition of new type

[codecov]

Codecov Report

Merging #1226 (5dee7da) into develop (dbcf65b) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##           develop     #1226   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           37        37           
  Lines         2161      2161           
  Branches       660       660           
=========================================
  Hits          2161      2161           

Flag	Coverage Δ
unit	100.00% <100.00%> (ø)

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Impacted Files	Coverage Δ
lib/collection/variable.js	100.00% <100.00%> (ø)

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