feat: Pass methodName to Cordova Method

[EinfachHans]

I'm submitting a ... (check one with "x")

• bug report
• feature request
• support request => Please do not submit support requests here, use one of these channels: https://forum.ionicframework.com/ or https://ionicworldwide.herokuapp.com/

Current behavior:

Currently the created Provider uses the method of the written Method as Method-Name for the Cordova Plugin.

Expected behavior:

Would be great to pass the methodName via the CordovaOptions.

Why Hans, why?
Let me explain why i want this: Currently the Cordova HTTP Plugin changed their logic a bit to be able to abort outgoing HTTP Requests. Now the methods can return a request id. So if we would change the Plugin to work like this, the Method must be sync and callbacks must be given as Param. That's a huge effort for users who don't need it like this (btw. i personally like Promise-based Stuff way more). But not doing it is also not good, simple because this cool function is missing then.

So my Idea would be to clone all methods, for example a second method for:

@Cordova()
post(url: string, body: any, headers: any): Promise<HTTPResponse> {
  return;
}

would be

@Cordova({
  methodName: 'post',
  sync: true
})
postSync(url: string, body: any, headers: any,
       success: (result: HTTPResponse) => void, failure: (error: any) => void): string {
  return;
}

I already created a PR, because this is only a small change i think: #3558