Replace `go.uber.go/atomic` with Go standard library `sync/atomic`

Summary

We currently have a linter rule that blocks usage of sync/atomic and forces us to use go.uber.go/atomic instead. This rule was originally added because sync/atomic required atomic operations on primitive types, which was considered error-prone.

However, since Go 1.19, the standard library sync/atomic package now includes typed wrappers (e.g., atomic.Uint32, atomic.Int64, atomic.Bool, etc.) that provide the same safety guarantees as go.uber.go/atomic. This makes the uber package redundant.

Context

Prometheus is also making this transition:

• Issue: https://github.com/prometheus/prometheus/issues/14866
• PR: https://github.com/prometheus/prometheus/pull/18009

Proposed Changes

1. Remove the linter rule that blocks sync/atomic
2. Migrate all go.uber.go/atomic usage to the standard library sync/atomic typed wrappers
3. Configure a linter rule to block the old-style atomic functions that operate on primitive types (e.g., atomic.AddInt64, atomic.LoadUint32) to ensure we only use the new typed wrappers and avoid accidental misuse

This approach gives us:

• Fewer external dependencies
• Alignment with the broader Go ecosystem
• Same safety guarantees we had with uber/atomic

References

• Go 1.19 release notes on atomic types: https://tip.golang.org/doc/go1.19#atomic_types
• sync/atomic package docs: https://pkg.go.dev/sync/atomic