Ignore Links with invalid span context

[fbogsany]

See open-telemetry/opentelemetry-specification#1492.

In the following code we should check that the links each have a valid span context, and remove any with an invalid span context.

opentelemetry-ruby/sdk/lib/opentelemetry/sdk/trace/span.rb

Lines 327 to 344 in f6d1563

	def trim_links(links, max_links_count, max_attributes_per_link) # rubocop:disable Metrics/AbcSize, Metrics/CyclomaticComplexity, Metrics/PerceivedComplexity
	# Fast path (likely) common cases.
	return nil if links.nil?
	if links.size <= max_links_count &&
	links.all? { |link| link.attributes.size <= max_attributes_per_link && Internal.valid_attributes?(link.attributes) }
	return links.frozen? ? links : links.clone.freeze
	end
	# Slow path: trim attributes for each Link.
	links.last(max_links_count).map! do |link|
	attrs = Hash[link.attributes] # link.attributes is frozen, so we need an unfrozen copy to adjust.
	attrs.keep_if { |key, value| Internal.valid_key?(key) && Internal.valid_value?(value) }
	excess = attrs.size - max_attributes_per_link
	excess.times { attrs.shift } if excess.positive?
	OpenTelemetry::Trace::Link.new(link.span_context, attrs)
	end.freeze
	end