Add Proof of Concept(POC) for Collection Runner and Performance Load Testing Features

[tihom4537]

This PR introduces two major features to enhance API testing capabilities:

1. Collection Runner
   Implemented a create collection option and collection runner that enables environment-aware execution of API test collections. This feature allows users to:

Execute collections with configurable test parameters (iterations, delays, selected requests)
Track real-time progress during test runs
View detailed results with 8 key metrics per request
Navigate seamlessly to analysis tools after completion

The collection runner is built with Riverpod for state management and follows a sequential execution model in this initial implementation.
2. Performance Load Testing
Added a powerful API load testing tool that simulates real-world traffic patterns to evaluate system performance under load. Key capabilities include:

Configurable virtual user counts and test durations
Intelligent ramp-up implementation to gradually increase load
Concurrent request simulation mirroring actual user behavior
Comprehensive metrics collection (throughput, latency, error rates)
Real-time calculation of performance statistics

These features significantly enhance our application's testing capabilities, allowing users to not only validate API functionality but also assess performance characteristics under various load scenarios.
Related Issues

Related #100

Checklist

I have gone through the contributing guide
I have updated my branch and synced it with project main branch before making this PR
I am using the latest Flutter stable branch (run flutter upgrade and verify)
I have run the tests (flutter test) and all tests are passing

Added/updated tests?

Yes

OS on which you have developed and tested the feature?
macOS

[tihom4537]

Greetings @ashitaprasad, @animator,
I apologize for the delay in delivering this POC. I was involved in my college's technical fest, which took more of my time than anticipated.
Regarding the workflow builder canvas - I've completed the display component, but the execution functionality still requires additional work. I plan to submit that as a separate PR to keep the changes focused and easier to review.
Thank you for your patience and understanding.

[tihom4537]

Hi @ashitaprasad , @animator ,
I just wanted to follow up on the PR I submitted two days ago regarding the Collection Runner and Performance Load Testing features. If you have any feedback or if there are any changes you'd like me to make to the current implementation, I'd be happy to address them.

[tihom4537]

Additionally, I mentioned in my comment that I've completed the display component for the workflow builder canvas and is working on the execution engine of the workflow ,so was planning to submit them as a separate PR. Would you like me to proceed with creating that PR now, or would you prefer I wait until the current one is reviewed?
Thank you for your time, and I look forward to your guidance.