Add enforcement of AttributeValues for trace events

[toumorokoshi]

Right now, AttributeValues in span tags are supposed to be one of (int, bool, float), but we do no enforcement of that value when added.

This then requires error handling to be put into the exporters themselves, which will become fairly redundant: https://github.com/open-telemetry/opentelemetry-python/pull/320/files/93331ff73905ab0dad11110bdac45737098c2d26#r360226796

It would be great if we could enforce the types of attributes when added instead.

[jakemalachowski]

I'll take this one. Can this be assigned to me to avoid duplicating work?

[ocelotl]

Done! Thanks, @jakemalachowski 👍

[dgzlopes]

With #348 merged I think that this issue can be closed!

[mauriciovasquezbernal]

@dgzlopes not actually, #348 was about span attributes, this one is about attributes in Event:

opentelemetry-python/opentelemetry-sdk/src/opentelemetry/sdk/trace/__init__.py

Lines 268 to 280 in a7535a1

	def add_event(
	self,
	name: str,
	attributes: types.Attributes = None,
	timestamp: Optional[int] = None,
	) -> None:
	self.add_lazy_event(
	trace_api.Event(
	name,
	Span.empty_attributes if attributes is None else attributes,
	time_ns() if timestamp is None else timestamp,
	)
	)

[codeboten]

Closed by #678