[release/6.0] Remove two async state machines for typical HTTP/1.1 request path

[github-actions]

Backport of #58092 to release/6.0

Rather than having a dedicated async method for SendAndProcessAltSvcAsync, we can just have the sole call site call DetermineVersionAndSendAsync and ProcessAltSvc. And in DetermineVersionAndSendAsync, special-case the default configuration for SocketsHttpHandler that will result in HTTP/1.1 messages being sent, such that we avoid all the tests for HTTP/2 and HTTP/3 and the async state machine for DetermineVersionAndSendAsync when HTTP/1.1 is being requested and used.

This doesn't entirely get us back to the allocation profile of .NET 5, but it's much closer.

Method	Toolchain	Mean	Ratio	Allocated
Request	\5.0.9\corerun.exe	56.31 us	1.00	1,416 B
Request	\main\corerun.exe	56.60 us	1.01	1,888 B
Request	\pr\corerun.exe	54.84 us	0.97	1,464 B

I also noticed an unused parameter to the HTTP/2 and HTTP/3 try send async methods, so I removed those as well, removing those parameters from the corresponding state machines.

Best reviewed without whitespace diffing: https://github.com/dotnet/runtime/pull/58092/files?w=1

Fixes#57977

/cc @stephentoub

Customer Impact

A simple HTTP/1.1 request made with SocketsHttpHandler allocated 1,416 bytes in .NET 5. In release/6.0 currently, that same request allocates 33% more. This changes drops that to almost noise, at just 3% more.

Testing

CI

Risk

Low. Logic didn't change; code was just moved between between async methods, getting rid of several.

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Issue Details

---

Backport of #58092 to release/6.0

/cc @stephentoub

Customer Impact

Testing

Risk

Author:	github-actions[bot]
Assignees:	-
Labels:	area-System.Net.Http
Milestone:	-

[stephentoub]

cc: @danmoseley

[danmoseley]

Approved, as fixing significant regression to mainstream scenario with "low" risk.