fix: export tls key as pkcs8

The WebCrypto polyfill has [improved it's validation](PeculiarVentures/webcrypto-core@4ef9eaa) and we now fail to export the private key of the generated cert correctly.

Update to export in pkcs8 format instead, which we can just base64 encode to turn it into the PEM format.

packages/connection-encrypter-tls/src/utils.ts

@@ -179,11 +179,11 @@ export async function generateCertificate (peerId: PeerId): Promise<{ cert: stri
     ]
   })
 
-  const certPrivateKeySpki = await crypto.subtle.exportKey('spki', keys.privateKey)
+  const certPrivateKeyPkcs8 = await crypto.subtle.exportKey('pkcs8', keys.privateKey)
 
   return {
     cert: selfCert.toString(),
-    key: spkiToPEM(certPrivateKeySpki)
+    key: pkcs8ToPEM(certPrivateKeyPkcs8)
   }
 }
 
@@ -213,7 +213,7 @@ export function encodeSignatureData (certPublicKey: ArrayBuffer): Uint8Array {
   ])
 }
 
-function spkiToPEM (keydata: ArrayBuffer): string {
+function pkcs8ToPEM (keydata: ArrayBuffer): string {
   return formatAsPem(uint8ArrayToString(new Uint8Array(keydata), 'base64'))
 }