feat: Update options

[budde377]

This PR improves equality checks on options by making options immutable and supports the operator==. This is used to decide if the queries should be re-fetched.

The PR contains:

• Mark all options as immutable with @immutable.
• New copy helpers used by #1034 and this PR to prevent updates on the options.
• Switches from .equals to operator== to compare equality

[codecov[bot]]

Codecov Report

Merging #1037 (8aaf9d6) into beta (05ca62a) will increase coverage by 1.16%. The diff coverage is 49.31%.

:exclamation: Current head 8aaf9d6 differs from pull request most recent head 3af3454. Consider uploading reports for the commit 3af3454 to get more accurate results

@@            Coverage Diff             @@
##             beta    #1037      +/-   ##
==========================================
+ Coverage   51.25%   52.42%   +1.16%     
==========================================
  Files          36       35       -1     
  Lines        1389     1505     +116     
==========================================
+ Hits          712      789      +77     
- Misses        677      716      +39     

Impacted Files	Coverage Δ
...ackages/graphql/lib/src/core/observable_query.dart	40.32% <0.00%> (-0.67%)	:arrow_down:
packages/graphql/lib/src/core/query_manager.dart	66.87% <0.00%> (ø)
packages/graphql/lib/src/core/query_options.dart	39.28% <44.94%> (+13.83%)	:arrow_up:
...ackages/graphql/lib/src/core/mutation_options.dart	40.98% <48.27%> (+7.65%)	:arrow_up:
packages/graphql/lib/src/graphql_client.dart	74.28% <88.88%> (+1.31%)	:arrow_up:
packages/graphql/lib/src/core/_base_options.dart	87.50% <90.90%> (+29.43%)	:arrow_up:
packages/graphql/lib/src/core/policies.dart	57.81% <0.00%> (+10.93%)	:arrow_up:

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