Removes user_inputs field from Template and Global Context Index mapping

[joshpalis]

Description

This PR achieves the following :

• Modifies Global Context Index Mapping to remove user_inputs field
• Modifies Global Context Index Mapping to change workflows, user_outputs and resources_created fields to type object instead of text to support indexing dynamic json objects
• Removes special handling of reading/writing Template objects to the GC index and replacing each instance with Template::parse / Template::toXContent
• Fixes affected test classes

I prefer to merge this in prior to #106

Issues Resolved

Part of #88
#105

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[codecov]

Codecov Report

Merging #111 (dace266) into main (63ef780) will decrease coverage by 0.99%.
The diff coverage is 100.00%.

❗ Current head dace266 differs from pull request most recent head 34b071b. Consider uploading reports for the commit 34b071b to get more accurate results

@@             Coverage Diff              @@
##               main     #111      +/-   ##
============================================
- Coverage     81.46%   80.47%   -0.99%     
+ Complexity      285      252      -33     
============================================
  Files            30       30              
  Lines          1122      973     -149     
  Branches        126       98      -28     
============================================
- Hits            914      783     -131     
+ Misses          162      155       -7     
+ Partials         46       35      -11     

Files	Coverage Δ
...ch/flowframework/indices/GlobalContextHandler.java	72.22% <100.00%> (ø)
...a/org/opensearch/flowframework/model/Template.java	88.80% <ø> (+1.52%)	⬆️
...rk/transport/ProvisionWorkflowTransportAction.java	45.61% <100.00%> (ø)

... and 1 file with indirect coverage changes