[Access] Implement integration test for new websockets

[UlyanaAndrukhiv]

Closes: #6641

Note: This PR should be reviewed and merged only after the following PRs are merged:

• [Access] Make response for data providers consistent. #6846
• [Access] Unify subscription id with client message id #6847
• [Access] Add arguments getter for data providers #6873
• [Access] Implement subscribe transaction statuses by transaction ID [WIP] #6737

Context

This pull request adds integration tests to verify the functionality of the new WebSockets implementation. The tests cover the following scenarios:

1. Happy paths:

• Subscribing to any topic, ensuring a successful subscription response and expected results.
• Unsubscribing from a topic successfully.

2. Error cases:

• Attempting to subscribe with invalid data.
• Attempting to unsubscribe with invalid data.

3. Additional behaviors:

• Retrieving a list of all active subscriptions.
• Verifying client inactivity tracking and connection loss handling.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 54.41176% with 248 lines in your changes missing coverage. Please review.

Project coverage is 41.00%. Comparing base (0d2b34f) to head (b5b9f2f).
Report is 17 commits behind head on master.

Files with missing lines	Patch %	Lines
.../access/rpc/backend/backend_stream_transactions.go	63.35%	39 Missing and 9 partials ⚠️
storage/mock/batch.go	0.00%	46 Missing ⚠️
storage/mock/db.go	0.00%	44 Missing ⚠️
engine/access/rest/websockets/controller.go	68.67%	23 Missing and 3 partials ⚠️
engine/access/rest/common/utils.go	47.91%	24 Missing and 1 partial ⚠️
engine/access/rest/websockets/subscription_id.go	52.17%	8 Missing and 3 partials ⚠️
...st/websockets/data_providers/mock/data_provider.go	47.05%	6 Missing and 3 partials ⚠️
engine/access/rest/util/converter.go	0.00%	8 Missing ⚠️
...ckets/data_providers/mock/data_provider_factory.go	25.00%	3 Missing and 3 partials ⚠️
.../rest/websockets/data_providers/events_provider.go	61.53%	4 Missing and 1 partial ⚠️
... and 10 more

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #6907      +/-   ##
==========================================
- Coverage   41.11%   41.00%   -0.11%     
==========================================
  Files        2116     2122       +6     
  Lines      185737   185912     +175     
==========================================
- Hits        76368    76240     -128     
- Misses     102952   103255     +303     
  Partials     6417     6417              

Flag	Coverage Δ
unittests	41.00% <54.41%> (-0.11%)	⬇️

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