feat: Convert raw bytes or tlsfingerprint record to ClientHelloSpec (#168)

* feat: byte to clienthellospecs conversion

* feat: specific case for GREASE and ALPS

Will automatically add "h2" to ALPS and write to log when GREASE extension is imported in `ImportTLSClientHello()`

* fix: ReadCompressionMethods

ReadCompressionMethods didn't advance the s and fails reading extensions

* fix: remove debug log

* fix: use cryptobyte for internal helper

`helper.Uint8to16()` now calls `(*cryptobyte.String).ReadUint16()`

* fix: preshared key fingerprinter test

updated fingerprinter test to test with PreSharedKey extension

* fix: naming of FakePreSharedKeyExt

It is a Fake extension since `crypto/tls` doesn't really implement PSK-based resumption and neither do we.

* feat: Properly check GREASE

Adopted from #148.

Co-Authored-By: gfw-report <gfw.report@protonmail.com>

* feat: add fakeExtensionEncryptThenMAC

And reordered `fakeExtensionDelegatedCredentials`.

The new `Fingerprinter` is expected to account for the `fakeExtensionEncryptThenMAC` using a `GenericExtension` when `allowBluntMimicry` is set.

Co-Authored-By: gfw-report <gfw.report@protonmail.com>

* fix: remove keepPSK and minor

- Removed all presence of keepPSK flag.
- Added check before using the field of a map.

---------

Co-authored-by: gfw-report <gfw.report@protonmail.com>

internal/helper/typeconv.go

@@ -0,0 +1,23 @@
+package helper
+
+import (
+	"errors"
+
+	"golang.org/x/crypto/cryptobyte"
+)
+
+// Uint8to16 converts a slice of uint8 to a slice of uint16.
+// e.g. []uint8{0x00, 0x01, 0x00, 0x02} -> []uint16{0x0001, 0x0002}
+func Uint8to16(in []uint8) ([]uint16, error) {
+	s := cryptobyte.String(in)
+	var out []uint16
+	for !s.Empty() {
+		var v uint16
+		if s.ReadUint16(&v) {
+			out = append(out, v)
+		} else {
+			return nil, errors.New("ReadUint16 failed")
+		}
+	}
+	return out, nil
+}