Migrate all layers to context based

As discussed in https://github.com/apache/opendal/issues/5480, we will migrate OpenDAL to a context-based approach. Layers will be migrated too, allowing us to add metrics and timeouts based on the HTTP client instead.

## TODO

This issue is not ready for contributing. I will implement an example first.

## Tasks

- [ ] async_backtrace
- [ ] await_tree
- [x] concurrent_limit: https://github.com/apache/opendal/pull/6025
- [ ] dtrace
- [ ] fastrace
- [ ] logging
- [ ] oteltrace
- [x] tracing: https://github.com/apache/opendal/issues/5999

Start by reading the context in issue #5480 and the example implementation requested in this issue; no source files or tests are named yet. The migration is not ready for contribution, and done would mean completing the unchecked layer tasks while preserving the linked concurrent_limit and tracing work.

Written by the indexing model from the issue text.