## Problem
Some feature flags are used heavily on the critical path and we want the
"get feature flag" operation as cheap as possible.
## Summary of changes
Add a `test_remote_size_flag` as an example of such flags. In the
future, we can use macro to generate all those fields. The flag is
updated in the housekeeping loop. The retrieval of the flag is simply
reading an atomic flag.
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Signed-off-by: Alex Chi Z <chi@neon.tech>
a06c560ad0