Unify setting the options for the object store's http client

[MichaelScofield]

What type of enhancement is this?

Configuration

What does the enhancement do?

Now the options for the object store's http client are set like this:

let connect_timeout = env::var("_GREPTIMEDB_HTTP_CONNECT_TIMEOUT")
    .ok()
    .and_then(|v| v.parse::<u64>().ok())
    .unwrap_or(30);
builder = builder.connect_timeout(Duration::from_secs(connect_timeout));

It's better to make them set from the config file instead, like this:

[[storage.providers]]
name = "S3"
type = "S3"
timeout = "30s"
# ...

Implementation challenges

No response

[CookiePieWw]

As we introduced settings for http clients in #5041, we can close this?

[evenyag]

@MichaelScofield Maybe we can remove the env options in the next release.

@CookiePieWw We can keep this open to remind us to remove them.