ci: update Codecov configuration for test and coverage upload
- Unified usage of `codecov/codecov-action@v5` for both test results and
coverage upload.
- Added `CODECOV_TOKEN` and `report_type` parameters for improved
configuration.
## Motivation and Context
Actually, CODECOV_TOKEN is required, even though the CodeCov banner
previously said the project can upload without a token.
## How Has This Been Tested?
CI
## Breaking Changes
No
## Types of changes
- [x] CI fix
## Checklist
<!-- Go over all the following points, and put an `x` in all the boxes
that apply. -->
- [x] I have read the [MCP
Documentation](https://modelcontextprotocol.io)
- [x] My code follows the repository's style guidelines
- [x] New and existing tests pass locally
- [ ] I have added appropriate error handling
- [ ] I have added or updated documentation as needed
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