Do not load Datadog tracing when dogstatsd is present

See merge request !361

also, fixed some of the arithmetic associated with logging timeout logs

adding support for ruby 3.4

See merge request !360

nodejs servers, for example, seem to send them when shutting down servers on timeout; when receiving, in the same buffer, the first correctly closes the parser and emits the message, while the second, because the parser is closed already, will emit an exception; the regression happened because the second exception was swallowed by the pool handler, but now that's gone, and errors on connection consumption get handled; this was worked around by, on the parser, when emitting the errors for pending requests, claearing the queue, as when the second error comes, there's no request to emit the error for

Closes #333

fix: handle multi goaway frames coming from server

Closes #333

See merge request !362

this was previously done in connection initialization, which means that the request would map to an error response with this error; however, the change to thread-safe pools in 1.4.0 caused a regression, where the uri is expected to have an origin before the connection is established; this is fixed by raising an error on request creation, which will need to be caught by the caller

Fixes #335

raise error when httpx is used with an url not starting with http or https schemes

Closes #335

See merge request !366

```
/usr/local/bundle/gems/httpx-1.4.0/lib/httpx/selector.rb:95: warning: method redefined; discarding old empty?
/usr/local/lib/ruby/3.4.0/forwardable.rb:231: warning: previous definition of empty? was here
/usr/local/bundle/gems/httpx-1.4.0/lib/httpx/resolver/system.rb:54: warning: method redefined; discarding old empty?
/usr/local/lib/ruby/3.4.0/forwardable.rb:231: warning: previous definition of empty? was here
```

In selector.rb, the definitions are identical, so I kept the delegator

For system.rb, it always returns true so I kept that one

Fix two method redefinition warnings

See merge request !367

also, made the handler a bit more functional style, which curbs some of the complexity

faraday sets it as float and it doesn't seem to break because of it)

and not from the request object, which reproduces the bug

the headers were being set on the request object after the request was buffered and sent

datadog plugin fixes

See merge request !364

instead of implementing method missing; this makes it simpler impl-wise, and it'll also make comparing types easier, although not needed ATM

there's a bug (reported in https://bugs.ruby-lang.org/issues/21131) with IO.copy_stream, where yielded duped strings still change value on subsequent yields, which breaks http2 framing, which requires two yields at the same time in the first iteration. it replaces it with #read calls; file handles will now be closed once done streaming, which is a change in behaviour

one of them being the otel plugin, see https://github.com/open-telemetry/opentelemetry-ruby-contrib/pull/1404

IO.copy_stream changes yielded string on subsequent yields

Closes #338

See merge request !369

fix: do not schedule deferred HEv2 ipv4 tcp handshake if the connection has already been closed by the sibling connection

each connection will now check in its sibling and whether it's the original connection (containing the inital batch of requests); internal functions are then called to control how connections react to successful or failed resolutions, which reduces code repetition

the handling of coalesced connections is also simplified, as when that happens, the sibling must also be closed. this allowed to fix some mismatch when handling this use case with callbacks

continue resolving when an error happens by immediately writing to the buffer afterwards

by setting it in select_connection instead

resolver: early exit for closed connections later, after updating addresses (in case they ever get reused)