priority: use new-style atomic APIs (#8558)

Use new-style atomic APIs instead of the old ones in the
`ignoreResolveNowClientConn` type.

The changes made in this PR improve the code in the following ways:
* Ergonomics: Method-based API vs function-based, no pointer management
needed
* Safety: Type safety prevents mixing atomic/non-atomic operations,
eliminates pointer errors
* Clarity: The `atomic.Uint32` type makes atomic intent explicit from
declaration

RELEASE NOTES: none

Author: easwars

internal/xds/balancer/priority/ignore_resolve_now.go

@@ -29,29 +29,21 @@ import (
 // ResolveNow() method to ignore those calls if the ignoreResolveNow bit is set.
 type ignoreResolveNowClientConn struct {
 	balancer.ClientConn
-	ignoreResolveNow *uint32
+	ignoreResolveNow atomic.Bool
 }
 
 func newIgnoreResolveNowClientConn(cc balancer.ClientConn, ignore bool) *ignoreResolveNowClientConn {
-	ret := &ignoreResolveNowClientConn{
-		ClientConn:       cc,
-		ignoreResolveNow: new(uint32),
-	}
+	ret := &ignoreResolveNowClientConn{ClientConn: cc}
 	ret.updateIgnoreResolveNow(ignore)
 	return ret
 }
 
 func (i *ignoreResolveNowClientConn) updateIgnoreResolveNow(b bool) {
-	if b {
-		atomic.StoreUint32(i.ignoreResolveNow, 1)
-		return
-	}
-	atomic.StoreUint32(i.ignoreResolveNow, 0)
-
+	i.ignoreResolveNow.Store(b)
 }
 
-func (i ignoreResolveNowClientConn) ResolveNow(o resolver.ResolveNowOptions) {
-	if atomic.LoadUint32(i.ignoreResolveNow) != 0 {
+func (i *ignoreResolveNowClientConn) ResolveNow(o resolver.ResolveNowOptions) {
+	if i.ignoreResolveNow.Load() {
 		return
 	}
 	i.ClientConn.ResolveNow(o)