FLIP: Allow adding new fields to existing types

[turbolent]

Moved from onflow/flow#1097

Please see the initial discussion there

[SupunS]

👌

[turbolent]

cc @austinkline @bluesign @bjartek

[turbolent]

@austinkline We had a working group discussion about this FLIP yesterday, see https://github.com/onflow/Flow-Working-Groups/blob/main/cadence_language_and_execution_working_group/meetings/2024-10-29.md#flips.

Feedback has been that it is a low priority feature, and given the complicated situation (existing stored state with "removed" fields) and the dependency on first having to prevent field removal (for both, see https://github.com/onflow/flips/pull/295/files#diff-6243eb63ad4bcc7c53d3b54c65552ad22149247ebef272dbb0413115b04e989aR104-R116), there is unfortunately quite a lot of effort required to implement this FLIP.

Consensus has been that there are more important proposals to get in, and this proposal will be on hold, unless there is a strong reason to justify the effort. What do you think about this?