Update exception_list.hpp

[charan-003]

This exception_list class in the hpx namespace is a thread-safe container for handling multiple exceptions encountered during parallel algorithm execution. It allows storing std::exception_ptr objects, provides thread-safe access via a spinlock, and includes methods to add exceptions, get the count (size()), and iterate over the stored exceptions (begin()/end()). The class also includes placeholders for retrieving error codes and messages. This is useful for collecting and managing exceptions across parallel threads.

Fixes # [Issue Number]

Proposed Changes
Added exception_list class for managing exceptions in parallel execution
Implemented thread-safe methods for adding and accessing exceptions
Provided placeholders for error code and message retrieval
Any background context you want to provide?
This class addresses the need for managing multiple exceptions in parallel algorithms and ensures thread safety via hpx::spinlock. It simplifies exception handling in concurrent contexts.

Checklist
Not all points below apply to all pull requests.

I have added a new feature and have added tests to go along with it.
I have fixed a bug and have added a regression test.
I have added a test using random numbers; I have made sure it uses a seed, and that random numbers generated are valid inputs for the tests.

[StellarBot]

Can one of the admins verify this patch?

[hkaiser]

@charan-003 two questions:

• What is the use case that requires for the copy/move construction/assignment to be thread safe?
• Wouldn't it be better to modify the existing implementations for the functions instead of adding (now duplicate) ones?

[codacy-production]

Coverage summary from Codacy

See diff coverage on Codacy

Coverage variation	Diff coverage
✅ -85.50%	✅ 0.00%

Coverage variation details

	Coverable lines	Covered lines	Coverage
Common ancestor commit (5356c52)	234528	200611	85.54%
Head commit (5f31ce5)	120066 (-114462)	51 (-200560)	0.04% (-85.50%)

Coverage variation is the difference between the coverage for the head and common ancestor commits of the pull request branch: <coverage of head commit> - <coverage of common ancestor commit>

Diff coverage details

	Coverable lines	Covered lines	Diff coverage
Pull request (#6568)	34	0	0.00%

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[charan-003]

@hkaiser Could someone help me debug the CircleCI errors (build-and-test, clang_format, core, depreport, and inspect) on this pull request? Thank you!

[hkaiser]

@hkaiser Could someone help me debug the CircleCI errors (build-and-test, clang_format, core, depreport, and inspect) on this pull request? Thank you!

You have to log in to circleci using your github credentials to see the logs there.