* Add `ROCSHMEM_CTX_INVALID` for invalid context handling
- Define `ROCSHMEM_CTX_INVALID` as {nullptr, nullptr}
- Add == and != operators to rocshmem_ctx_t
- Use `ROCSHMEM_CTX_INVALID` on failed context creation
- Skip ctx destroy if context is invalid
* Update docs for context create and destroy APIs usage and behavior
* Refactor `Barrier_all` and `Sync_all` to use default context
- Removed context-specific implementations of barrier_all and sync_all
- Added barrier_all and sync_all to the default context implementation
- Updated functional tests to use the default context for barrier_all and sync_all
* Update `Barrier_all` and `Sync_all` API usage in documentation
* Update `CHANGELOG`
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Co-authored-by: Yiltan <ytemucin@amd.com>
Avinash Kethineedi
Yiltan
Aurelien Bouteiller
yugang-amd