Upgrade net package from Go 1.21.4 to Go 1.26.2

Backport upstream Go standard library changes to TinyGo's net package.

Unmodified files (18) replaced directly from Go 1.26.2 source.
Modified files (22) merged via 3-way diff, preserving all TinyGo
netdev adaptations, TINYGO markers, and embedded-device constraints.

Notable upstream changes included:
- net/http: cookie handling improvements, fs enhancements,
  reverse proxy updates, chunked encoding fixes
- net/http: ServeMux routing and pattern matching updates
- net: IP parsing and MAC address handling improvements
- Various doc link syntax modernization (e.g. [Dial], [Buffers])

TinyGo-only files (netdev.go, tlssock.go) unchanged.
All TINYGO comment markers preserved.

http/header.go

@@ -1,4 +1,4 @@
-// TINYGO: The following is copied and modified from Go 1.21.4 official implementation.
+// TINYGO: The following is copied and modified from Go 1.26.2 official implementation.
 
 // TINYGO: Removed trace stuff
 
@@ -12,7 +12,7 @@ import (
 	"io"
 	"net/http/internal/ascii"
 	"net/textproto"
-	"sort"
+	"slices"
 	"strings"
 	"sync"
 	"time"
@@ -23,13 +23,13 @@ import (
 // A Header represents the key-value pairs in an HTTP header.
 //
 // The keys should be in canonical form, as returned by
-// CanonicalHeaderKey.
+// [CanonicalHeaderKey].
 type Header map[string][]string
 
 // Add adds the key, value pair to the header.
 // It appends to any existing values associated with key.
 // The key is case insensitive; it is canonicalized by
-// CanonicalHeaderKey.
+// [CanonicalHeaderKey].
 func (h Header) Add(key, value string) {
 	textproto.MIMEHeader(h).Add(key, value)
 }
@@ -37,7 +37,7 @@ func (h Header) Add(key, value string) {
 // Set sets the header entries associated with key to the
 // single element value. It replaces any existing values
 // associated with key. The key is case insensitive; it is
-// canonicalized by textproto.CanonicalMIMEHeaderKey.
+// canonicalized by [textproto.CanonicalMIMEHeaderKey].
 // To use non-canonical keys, assign to the map directly.
 func (h Header) Set(key, value string) {
 	textproto.MIMEHeader(h).Set(key, value)
@@ -45,7 +45,7 @@ func (h Header) Set(key, value string) {
 
 // Get gets the first value associated with the given key. If
 // there are no values associated with the key, Get returns "".
-// It is case insensitive; textproto.CanonicalMIMEHeaderKey is
+// It is case insensitive; [textproto.CanonicalMIMEHeaderKey] is
 // used to canonicalize the provided key. Get assumes that all
 // keys are stored in canonical form. To use non-canonical keys,
 // access the map directly.
@@ -54,7 +54,7 @@ func (h Header) Get(key string) string {
 }
 
 // Values returns all values associated with the given key.
-// It is case insensitive; textproto.CanonicalMIMEHeaderKey is
+// It is case insensitive; [textproto.CanonicalMIMEHeaderKey] is
 // used to canonicalize the provided key. To use non-canonical
 // keys, access the map directly.
 // The returned slice is not a copy.
@@ -79,7 +79,7 @@ func (h Header) has(key string) bool {
 
 // Del deletes the values associated with key.
 // The key is case insensitive; it is canonicalized by
-// CanonicalHeaderKey.
+// [CanonicalHeaderKey].
 func (h Header) Del(key string) {
 	textproto.MIMEHeader(h).Del(key)
 }
@@ -128,7 +128,7 @@ var timeFormats = []string{
 
 // ParseTime parses a time header (such as the Date: header),
 // trying each of the three formats allowed by HTTP/1.1:
-// TimeFormat, time.RFC850, and time.ANSIC.
+// [TimeFormat], [time.RFC850], and [time.ANSIC].
 func ParseTime(text string) (t time.Time, err error) {
 	for _, layout := range timeFormats {
 		t, err = time.Parse(layout, text)
@@ -155,17 +155,11 @@ type keyValues struct {
 	values []string
 }
 
-// A headerSorter implements sort.Interface by sorting a []keyValues
-// by key. It's used as a pointer, so it can fit in a sort.Interface
-// interface value without allocation.
+// headerSorter contains a slice of keyValues sorted by keyValues.key.
 type headerSorter struct {
 	kvs []keyValues
 }
 
-func (s *headerSorter) Len() int           { return len(s.kvs) }
-func (s *headerSorter) Swap(i, j int)      { s.kvs[i], s.kvs[j] = s.kvs[j], s.kvs[i] }
-func (s *headerSorter) Less(i, j int) bool { return s.kvs[i].key < s.kvs[j].key }
-
 var headerSorterPool = sync.Pool{
 	New: func() any { return new(headerSorter) },
 }
@@ -185,7 +179,7 @@ func (h Header) sortedKeyValues(exclude map[string]bool) (kvs []keyValues, hs *h
 		}
 	}
 	hs.kvs = kvs
-	sort.Sort(hs)
+	slices.SortFunc(hs.kvs, func(a, b keyValues) int { return strings.Compare(a.key, b.key) })
 	return kvs, hs
 }