ssl_client2: Add Host to HTTP GET request

[jetm]

Description

If an IP address shares multiple domain names with different SSL certificates and makes a GET request without the remote server name (host), it will fail with a 421 Misdirect Request.

Please read https://github.com/Mbed-TLS/mbedtls/issues/9093 for more details on how to reproduce the problem that this PR is addressing and further details.

PR checklist

Please tick as appropriate and edit the reasons (e.g.: "backport: not needed because this is a new feature")

• [ ] ~~changelog provided~~. Not required. Please let me know if it's required to update the changelog.
• [X] 3.6 backport.
• [ ] ~~2.28 backport~~. N/A
• [ ] tests provided. Waiting on CI results

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