Middleware proxy doesn't change the host header so can't be used with an API on a shared IP

[djay]

Describe the bug
The middleware proxy in volto breaks with a connection refused if you the api path is set to api that uses the host header to direct the request.

To Reproduce

1. Deploy the plone backend behind a proxy that uses a host header to direct the request. Say api.myapp
2. Deploy the volto frontend to www.myapp and set the RAZZLE_API_PATH=https://api.myapp
3. Requests to https://api.myapp/++api++ will fail (because they will be sent with "Host: www.myapp" not "Host: api.myapp".

Expected behavior

Set the right host header.

volto/packages/volto/src/express-middleware/devproxy.js

Line 49 in a34da0b

onProxyReq: (proxyReq, req, res) => {

Should also probably set X-Forwarded-Host etc - https://jdudzik.medium.com/posthog-reverse-proxy-with-node-express-js-480c1372f608

Screenshots
N/A

Software (please complete the following information):

• OS: [e.g. iOS]
• Browser [e.g. chrome, safari]
• Volto Version [e.g. 8.5.0]
• Plone Version [e.g. 5.2.2]
• Plone REST API Version [e.g. 7.0.1]

Additional context
Add any other context about the problem here.