TUN-8052: Update go to 1.21.5

Also update golang.org/x/net and google.golang.org/grpc to fix vulnerabilities,
although cloudflared is using them in a way that is not exposed to those risks

vendor/google.golang.org/grpc/internal/envconfig/envconfig.go

@@ -21,19 +21,49 @@ package envconfig
 
 import (
 	"os"
+	"strconv"
 	"strings"
 )
 
-const (
-	prefix                  = "GRPC_GO_"
-	txtErrIgnoreStr         = prefix + "IGNORE_TXT_ERRORS"
-	advertiseCompressorsStr = prefix + "ADVERTISE_COMPRESSORS"
-)
-
 var (
 	// TXTErrIgnore is set if TXT errors should be ignored ("GRPC_GO_IGNORE_TXT_ERRORS" is not "false").
-	TXTErrIgnore = !strings.EqualFold(os.Getenv(txtErrIgnoreStr), "false")
+	TXTErrIgnore = boolFromEnv("GRPC_GO_IGNORE_TXT_ERRORS", true)
 	// AdvertiseCompressors is set if registered compressor should be advertised
 	// ("GRPC_GO_ADVERTISE_COMPRESSORS" is not "false").
-	AdvertiseCompressors = !strings.EqualFold(os.Getenv(advertiseCompressorsStr), "false")
+	AdvertiseCompressors = boolFromEnv("GRPC_GO_ADVERTISE_COMPRESSORS", true)
+	// RingHashCap indicates the maximum ring size which defaults to 4096
+	// entries but may be overridden by setting the environment variable
+	// "GRPC_RING_HASH_CAP".  This does not override the default bounds
+	// checking which NACKs configs specifying ring sizes > 8*1024*1024 (~8M).
+	RingHashCap = uint64FromEnv("GRPC_RING_HASH_CAP", 4096, 1, 8*1024*1024)
+	// LeastRequestLB is set if we should support the least_request_experimental
+	// LB policy, which can be enabled by setting the environment variable
+	// "GRPC_EXPERIMENTAL_ENABLE_LEAST_REQUEST" to "true".
+	LeastRequestLB = boolFromEnv("GRPC_EXPERIMENTAL_ENABLE_LEAST_REQUEST", false)
+	// ALTSMaxConcurrentHandshakes is the maximum number of concurrent ALTS
+	// handshakes that can be performed.
+	ALTSMaxConcurrentHandshakes = uint64FromEnv("GRPC_ALTS_MAX_CONCURRENT_HANDSHAKES", 100, 1, 100)
 )
+
+func boolFromEnv(envVar string, def bool) bool {
+	if def {
+		// The default is true; return true unless the variable is "false".
+		return !strings.EqualFold(os.Getenv(envVar), "false")
+	}
+	// The default is false; return false unless the variable is "true".
+	return strings.EqualFold(os.Getenv(envVar), "true")
+}
+
+func uint64FromEnv(envVar string, def, min, max uint64) uint64 {
+	v, err := strconv.ParseUint(os.Getenv(envVar), 10, 64)
+	if err != nil {
+		return def
+	}
+	if v < min {
+		return min
+	}
+	if v > max {
+		return max
+	}
+	return v
+}