Respect the 'origin' setting in a non-browser environment

[matmilbury]

It bothers me I can't set origin when connecting with frame.

More precisely, I can set it but it's ignored by eth-provider:

eth-provider/connections/http.js

Lines 114 to 115 in 99c3c98

	// Below not working becasue XHR lib blocks it claiming "restricted header"
	// if (this.options.origin) xhr.setRequestHeader('Origin', this.options.origin)

Now, I know in a browser environment sets this for a correct value and a user can't do that programmaticaly.

But in node environments (like a cli tool) we can and should set this up to have clarity which program requests a connection.

Therefore, we should:

try {
  if (this.options.origin) xhr.setRequestHeader('Origin', this.options.origin)
} catch {
  // browser environment will set this to the correct value
}

@floating I can create a PR if you want?