Add support for apiMaturity key for <cluster> entries in XML

[andy31415]

This adds an API maturity level for cluster entries in XMLs so we can mark provisional, deprecated and internal items.

Intent is to have all of cluster, bitmap, bitmap-fields, struct, struct-item, attribute, command, command-arg, event, event-field, enum, enum-item suppor this.

Changes:

• DB backing for the new field
• Insert new field during xml parsing
• Expose new field during quering and constructing of objects
• Ensure .zap file output contains the apiMaturity information
• Update DTD schema DTD could be updated for validation of content
• Add unit tests (created a separate test suite)
• Ensure that .zap file input will load the apiMaturity information - unit test uses zap file

Changes I did NOT know how to do:

• API Documentation: did not find where things are documented, assuming it is not, like is_singleton

[codecov-commenter]

Codecov Report

Merging #1166 (f52888b) into master (331ce9d) will increase coverage by 0.00%.
The diff coverage is 80.00%.

@@           Coverage Diff           @@
##           master    #1166   +/-   ##
=======================================
  Coverage   65.37%   65.38%           
=======================================
  Files         171      171           
  Lines       18362    18366    +4     
  Branches     3968     3969    +1     
=======================================
+ Hits        12005    12008    +3     
- Misses       6357     6358    +1     

Files	Coverage Δ
src-electron/db/db-mapping.js	98.80% <ø> (ø)
src-electron/db/query-cluster.js	92.85% <ø> (ø)
src-electron/db/query-endpoint-type.js	89.65% <ø> (ø)
src-electron/db/query-loader.js	98.89% <ø> (ø)
src-electron/db/query-session-zcl.js	95.23% <ø> (ø)
src-electron/db/query-zcl.js	93.88% <ø> (ø)
src-electron/zcl/zcl-loader-silabs.js	94.43% <100.00%> (+<0.01%)	⬆️
src-electron/db/query-impexp.js	97.56% <75.00%> (-0.58%)	⬇️