Support TLSSocket.alpnProtocol in node:tls compat

[scotttrinh]

The TLSSocket.alpnProtocol property is referenced in the docs, but does not appear to actually exist:

deno/ext/node/polyfills/_tls_wrap.ts

Lines 62 to 78 in 66929de

	export class TLSSocket extends net.Socket {
	_tlsOptions: any;
	_secureEstablished: boolean;
	_securePending: boolean;
	_newSessionPending: boolean;
	_controlReleased: boolean;
	secureConnecting: boolean;
	_SNICallback: any;
	servername: string | null;
	alpnProtocols: string[] | null;
	authorized: boolean;
	authorizationError: any;
	[kRes]: any;
	[kIsVerified]: boolean;
	[kPendingSession]: any;
	[kConnectOptions]: any;
	ssl: any;

In Deno.TlsConn we have .handshake that will return the ALPN protocol selected during the handshake:

deno/ext/net/ops_tls.rs

Line 140 in 66929de

pub async fn handshake(

In Node, it is set on the TLSSocket instance:

https://github.com/nodejs/node/blob/4988bb549e79a6b92391b4ff529f675da32c0687/lib/_tls_wrap.js#L1063
https://github.com/nodejs/node/blob/4988bb549e79a6b92391b4ff529f675da32c0687/src/crypto/crypto_tls.cc#L2078-L2102