fix: custom json encoder for List and Map doesn't work correctly in `full` mode

[mbfakourii]

New Pull Request Checklist

• [x] I am not disclosing a vulnerability.
• [x] I am creating this PR in reference to an issue.

Issue Description

Solve the parseEncode problem in list and map

Related issue: https://github.com/parse-community/Parse-SDK-Flutter/issues/788

Approach

The full: full was added for when we use the list and map in parseEncode and toJson

TODOs before merging

• [ ] Add tests
• [ ] Add changes to documentation (guides, repository pages, in-code descriptions)
• [ ] A changelog entry

[parse-github-assistant[bot]]

Thanks for opening this pull request!

• 🎉 We are excited about your hands-on contribution!

[codecov[bot]]

Codecov Report

Base: 10.26% // Head: 10.67% // Increases project coverage by +0.40% :tada:

Coverage data is based on head (a471393) compared to base (14be107). Patch coverage: 100.00% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #789      +/-   ##
==========================================
+ Coverage   10.26%   10.67%   +0.40%     
==========================================
  Files          49       47       -2     
  Lines        2815     2810       -5     
==========================================
+ Hits          289      300      +11     
+ Misses       2526     2510      -16     

Impacted Files	Coverage Δ
packages/dart/lib/src/utils/parse_encoder.dart	56.66% <100.00%> (+20.00%)	:arrow_up:
packages/dart/lib/src/network/options.dart	0.00% <0.00%> (-50.00%)	:arrow_down:
...ackages/dart/lib/src/network/parse_live_query.dart	0.00% <0.00%> (-0.92%)	:arrow_down:
packages/flutter/lib/parse_server_sdk.dart	8.77% <0.00%> (ø)
packages/dart/lib/src/objects/parse_file.dart	0.00% <0.00%> (ø)
packages/dart/lib/src/objects/parse_user.dart	0.00% <0.00%> (ø)
packages/dart/lib/src/objects/parse_file_web.dart	0.00% <0.00%> (ø)
packages/dart/lib/src/objects/parse_file_base.dart	0.00% <0.00%> (ø)
...ackages/dart/lib/src/network/parse_dio_client.dart	0.00% <0.00%> (ø)
...ckages/dart/lib/src/network/parse_http_client.dart	5.12% <0.00%> (ø)
... and 9 more

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[mtrezza]

Could you please rephrase the PR title? It will become the changelog entry and a developer should be able to understand what this fixes without reading the PR.

[parse-github-assistant[bot]]

I will reformat the title to use the proper commit message syntax.

[mbfakourii]

Could you add a test to demonstrate what is not working correctly?

test added

[mbfakourii]

There's still a lint issue, not sure what it is, because the logs don't show any specific message. Do you have any idea?

It is for Dart code format I committed, it is probably fixed

[mtrezza]

Indeed, the tests pass, now we just need a review from @parse-community/flutter-sdk-review

[mtrezza]

There has been no additional review, but I'll go ahead and merge it anyway; if there is an issue, we'll find out.

Could you please:

1. Increment the dart version number (patch)
2. Add a changelog entry to the dart changelog with the title of this PR:

### Bug Fixes:
- Custom JSON encoder for List and Map doesn't work correctly in `full` mode (#789)