balancer: enable GRPC_GO_EXPERIMENTAL_CASE_SENSITIVE_BALANCER_REGISTRIES by default (#9017)

Part of #5288

Follow up of PR: #8837

This PR enabled the env variable
GRPC_GO_EXPERIMENTAL_CASE_SENSITIVE_BALANCER_REGISTRIES by default to
transition balancer registries to be case-sensitive.

RELEASE NOTES:
* balancer: balancer registries are now case-sensitive by default.
Disable GRPC_GO_EXPERIMENTAL_CASE_SENSITIVE_BALANCER_REGISTRIES env var
to temporarily revert this behavior.

Author: Pranjali-2501

balancer/balancer.go

@@ -60,7 +60,7 @@ func Register(b Builder) {
 	if !envconfig.CaseSensitiveBalancerRegistries {
 		name = strings.ToLower(name)
 		if name != b.Name() {
-			logger.Warningf("Balancer registered with name %q. grpc-go will be switching to case sensitive balancer registries soon. After 2 releases, we will enable the env var by default.", b.Name())
+			logger.Warningf("Balancer registered with name %q. grpc-go has switched to case sensitive balancer registries. GRPC_GO_EXPERIMENTAL_CASE_SENSITIVE_BALANCER_REGISTRIES env variable will be removed in release v1.82.0", b.Name())
 		}
 	}
 	m[name] = b
@@ -85,7 +85,7 @@ func Get(name string) Builder {
 	if !envconfig.CaseSensitiveBalancerRegistries {
 		lowerName := strings.ToLower(name)
 		if lowerName != name {
-			logger.Warningf("Balancer retrieved for name %q. grpc-go will be switching to case sensitive balancer registries soon. After 2 releases, we will enable the env var by default.", name)
+			logger.Warningf("Balancer retrieved for name %q. grpc-go has switched to case sensitive balancer registries. GRPC_GO_EXPERIMENTAL_CASE_SENSITIVE_BALANCER_REGISTRIES env variable will be removed in release v1.82.0", name)
 		}
 		name = lowerName
 	}

internal/envconfig/envconfig.go

@@ -78,12 +78,12 @@ var (
 	EnableDefaultPortForProxyTarget = boolFromEnv("GRPC_EXPERIMENTAL_ENABLE_DEFAULT_PORT_FOR_PROXY_TARGET", true)
 
 	// CaseSensitiveBalancerRegistries is set if the balancer registry should be
-	// case-sensitive. This is disabled by default, but can be enabled by setting
+	// case-sensitive. This is enabled by default, but can be disabled by setting
 	// the env variable "GRPC_GO_EXPERIMENTAL_CASE_SENSITIVE_BALANCER_REGISTRIES"
-	// to "true".
+	// to "false".
 	//
-	// TODO: After 2 releases, we will enable the env var by default.
-	CaseSensitiveBalancerRegistries = boolFromEnv("GRPC_GO_EXPERIMENTAL_CASE_SENSITIVE_BALANCER_REGISTRIES", false)
+	// This env varible will be removed in release v1.82.0.
+	CaseSensitiveBalancerRegistries = boolFromEnv("GRPC_GO_EXPERIMENTAL_CASE_SENSITIVE_BALANCER_REGISTRIES", true)
 
 	// XDSAuthorityRewrite indicates whether xDS authority rewriting is enabled.
 	// This feature is defined in gRFC A81 and is enabled by setting the