Template editor JSON exporting and importing

[zhang-yuanrui]

This PR fulfill 2 parts of functionalities:

1. Exporting templates with hierarchy into a JSON file by the interface get_templates_as_json
2. Importing a JSON file and build the templates from the JSON by the interface load_templates

Things not done yet in this PR:

1. Checking comprehensive user errors when loading a JSON file. I did some basic JSON format error checking but not exhaustive.
2. Prompting users if they want to rename when loading a root template with the same name as the existing one.

Please note that: in this PR, load_templates is supposed to be working when given a correct JSON input, ideally, the original / unchanged JSON file from get_templates_as_json

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 92.10526% with 6 lines in your changes missing coverage. Please review.

Project coverage is 60.56%. Comparing base (699d4d0) to head (4470afe).

Files with missing lines	Patch %	Lines
...ynamicreporting/core/utils/report_remote_server.py	92.10%	2 Missing and 4 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #207      +/-   ##
==========================================
+ Coverage   60.17%   60.56%   +0.39%     
==========================================
  Files          22       22              
  Lines        6626     6702      +76     
  Branches     1264     1280      +16     
==========================================
+ Hits         3987     4059      +72     
  Misses       2269     2269              
- Partials      370      374       +4     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.