Possible to add `_start_tls_compatible` attribute to `TCPTransport`?

• uvloop version: 0.19.0
• Python version: 3.10.7
• Platform: Linux
• Can you reproduce the bug with PYTHONASYNCIODEBUG in env?: Yes
• Does uvloop behave differently from vanilla asyncio? How?: Yes

aiohttp (3.9.1) keeps warning (falsely) about ^1

RuntimeWarning: An HTTPS request is being sent through an HTTPS proxy. This support for TLS in TLS is known to be disabled in the stdlib asyncio (Python <3.11). This is why you'll probably see an error in the log below.

It throws this warning because it's not able to find _start_tls_compatible property on the TCPTransport object (https://github.com/aio-libs/aiohttp/blob/v3.9.1/aiohttp/connector.py#L1054). The same property is present when asyncio is used which provides SelectorSocketTransport as the underlying transport. Is it possible to provide the _start_tls_compatible attribute on the TCPTransport which can help us avoid this warning?

Start by comparing uvloop's TCPTransport with asyncio's SelectorSocketTransport, then read the aiohttp connector reference linked in the issue to understand how _start_tls_compatible is checked. Done means TCPTransport exposes the compatibility attribute and aiohttp no longer emits the false TLS-in-TLS warning.