RecordException = true behavior in Http instrumentation

[vishweshbankwar]

Unit tests validating the behavior (i.e. whether the output span will contain the exception event) was added in open-telemetry/opentelemetry-dotnet#3761. Opening this issue to summarize the details and discuss any improvements that may be needed towards making the experience consistent. Following table summarizes the output for each method that was added in unit test.

Class Name	Method Name	Response code	Exception SpanEvent
HttpClient	GetAsync	Error response code	No
HttpClient	GetAsync	Network error	Yes
HttpClient	GetStringAsync	Network error	Yes
HttpClient	GetStringAsync	Error response code	No
WebRequest	GetResponseAsync	Error response code	Yes
WebRequest	GetResponseAsync	Network error	Yes