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.

parse.go

@@ -1,6 +1,4 @@
-// TINYGO: The following is copied from Go 1.21.4 official implementation.
-
-// Copyright 2009 The Go Authors. All rights reserved.
+// TINYGO: The following is copied from Go 1.26.2 official implementation.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
@@ -66,6 +64,14 @@ func (f *file) readLine() (s string, ok bool) {
 	return
 }
 
+func (f *file) stat() (mtime time.Time, size int64, err error) {
+	st, err := f.file.Stat()
+	if err != nil {
+		return time.Time{}, 0, err
+	}
+	return st.ModTime(), st.Size(), nil
+}
+
 func open(name string) (*file, error) {
 	fd, err := os.Open(name)
 	if err != nil {
@@ -174,42 +180,6 @@ func xtoi2(s string, e byte) (byte, bool) {
 	return byte(n), ok && ei == 2
 }
 
-// Convert i to a hexadecimal string. Leading zeros are not printed.
-func appendHex(dst []byte, i uint32) []byte {
-	if i == 0 {
-		return append(dst, '0')
-	}
-	for j := 7; j >= 0; j-- {
-		v := i >> uint(j*4)
-		if v > 0 {
-			dst = append(dst, hexDigit[v&0xf])
-		}
-	}
-	return dst
-}
-
-// Number of occurrences of b in s.
-func count(s string, b byte) int {
-	n := 0
-	for i := 0; i < len(s); i++ {
-		if s[i] == b {
-			n++
-		}
-	}
-	return n
-}
-
-// Index of rightmost occurrence of b in s.
-func last(s string, b byte) int {
-	i := len(s)
-	for i--; i >= 0; i-- {
-		if s[i] == b {
-			break
-		}
-	}
-	return i
-}
-
 // hasUpperCase tells whether the given string contains at least one upper-case.
 func hasUpperCase(s string) bool {
 	for i := range s {
@@ -281,23 +251,12 @@ func foreachField(x string, fn func(field string) error) error {
 	return nil
 }
 
-// stringsHasSuffix is strings.HasSuffix. It reports whether s ends in
-// suffix.
-func stringsHasSuffix(s, suffix string) bool {
-	return len(s) >= len(suffix) && s[len(s)-len(suffix):] == suffix
-}
-
 // stringsHasSuffixFold reports whether s ends in suffix,
 // ASCII-case-insensitively.
 func stringsHasSuffixFold(s, suffix string) bool {
 	return len(s) >= len(suffix) && stringsEqualFold(s[len(s)-len(suffix):], suffix)
 }
 
-// stringsHasPrefix is strings.HasPrefix. It reports whether s begins with prefix.
-func stringsHasPrefix(s, prefix string) bool {
-	return len(s) >= len(prefix) && s[:len(prefix)] == prefix
-}
-
 // stringsEqualFold is strings.EqualFold, ASCII only. It reports whether s and t
 // are equal, ASCII-case-insensitively.
 func stringsEqualFold(s, t string) bool {
@@ -311,17 +270,3 @@ func stringsEqualFold(s, t string) bool {
 	}
 	return true
 }
-
-func readFull(r io.Reader) (all []byte, err error) {
-	buf := make([]byte, 1024)
-	for {
-		n, err := r.Read(buf)
-		all = append(all, buf[:n]...)
-		if err == io.EOF {
-			return all, nil
-		}
-		if err != nil {
-			return nil, err
-		}
-	}
-}