Default context deadline to client timeout

[rkodev]

This change syncronizes the deafult context deadline and the client Timeout. When a user does not pass a context deadline, the default fallback will not be the value of the client timeout. This should also make it possible to modify default context deadlines for a single point addressing #70

Should also prevent the client timeout overriding the context timeout when its significantly lower microsoftgraph/msgraph-sdk-go#302 (comment)

To modify a deadline, you can pass initialize NetHttpRequestAdapter with a modified client.Timeout property.

client := GetDefaultClient()
client.Timeout = time.Second * 20

adapter := NewNetHttpRequestAdapterWithParseNodeFactoryAndSerializationWriterFactoryAndHttpClient(provider, nil, nil, client)

```

[sonarcloud]

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