Ignore SSL errors for HTTPS Requests

[harlem88]

Currently, the ignoreSSLErrors flag of the AstarteDevice constructor affects only the MQTTs connection.
This flag should also affect all internal HTTPS requests of Astarte SDK such as for the Pairing API.

Currently, the Astarte SDK throws an exception on HTTP side:

System.AggregateException: One or more errors occurred. (The SSL connection could not be established, see inner exception.)
System.Net.Http.HttpRequestException: The SSL connection could not be established, see inner exception.
System.Security.Authentication.AuthenticationException: The remote certificate is invalid because of errors in the certificate chain: UntrustedRoot
   at System.Net.Security.SslStream.SendAuthResetSignal(ReadOnlySpan`1 alert, ExceptionDispatchInfo exception)
   at System.Net.Security.SslStream.CompleteHandshake(SslAuthenticationOptions sslAuthenticationOptions)