docs: Prepare documentation for FireFly v1.3.0

[SamMayWork]

For 1.3 this contains the migration guide, along with updates to tutorials and docs to match the breaking changes going into this release. Do shout if there's anything I've missed

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 99.99%. Comparing base (4029c55) to head (824b681). Report is 5 commits behind head on main.

:exclamation: Current head 824b681 differs from pull request most recent head a11836a. Consider uploading reports for the commit a11836a to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1461      +/-   ##
==========================================
- Coverage   99.99%   99.99%   -0.01%     
==========================================
  Files         322      322              
  Lines       23406    23301     -105     
==========================================
- Hits        23404    23299     -105     
  Misses          1        1              
  Partials        1        1              

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