Fixed arun_many failing during deep crawling

[vikas-gits-good]

Summary

1. Fixed arun_many not working with DeepCrawlStrategy.
2. Fixed a silent bug where dispatch_result attribute of CrawlResult wasn't being updated correctly.

Fixes #1277

List of files changed and why

1. DeepCrawlDecorator in crawl4ai.deep_crawling.base_strategy was changed as it was returning a List[CrawlResultContainer] to arun_many which is an incompatible datatype. The data was flattened as explained in the issue comment.
2. arun_many in crawl4ai.async_webcrawler.AsyncWebCrawler was changed as the datatype needed further modification.
3. Also discovered that dispatch_result attribute of CrawlResult was not being updated. Fixed that as well.

How Has This Been Tested?

1. arun with deepcrawl=True | Status=working
2. arun with deepcrawl=False | Status=working
3. arun_many with dispatcher=MAD, deepcrawl=True | Status=working
4. arun_many with dispatcher=SD, deepcrawl=True | Status=working
5. arun_many with dispatcher=MAD, deepcrawl=False | Status=working
6. arun_many with dispatcher=SD, deepcrawl=False | Status=working
7. Haven't tested streaming combo. But that shouldn't matter as stream as a different pipeline.

Use this file to check.

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added/updated unit tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

[vikas-gits-good]

can you review it once?