Symfony version(s) affected: 4.4+

Description
Using the native HTTP client on php 7.3.22 and 7.4.10 produces the following error:

fopen(http://some/url): Failed to open stream: Failed to parse address "0"

How to reproduce
Run the test suite on php 7.3.22 or 7.4.10.

Possible Solution
Either:

• Change the default value for bindto in the contract from 0 to 0:0.
• Implement a workaround that removes bindto from the stream context is it has been set to 0.
• Implement a workaround that adds :0 is the port is missing.
• Fix php and restore the previous behavior.

Additional context
The problem seems to be that fopen fails if we provide an address without a port as bindto inside the stream context. This is unfortunate because HttpClient uses 0 as a default value, which means that if we don't explicitly set a value here, the request will fail. The default value is provided by the contract's ClientInterface. Changing it to 0:0 makes the tests pass again.

This change has been introduced with php 7.3.22/7.4.10. Running the test suite on php 7.3.21 or 7.4.9 works fine.