Update to Issue #389- Added ContextVars variable "association_properties_var"

[Daniel-Plops]

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Added a ContextVars variable to the TracerWrapper object such that it updates every time set_association_properties is called such that it stores a copy of the properties in a variable called association_properties_var, so changes are only stored when using the set_association_properties function. This allows for the properties to be viewed at certain instances in between trace updates so other functions could be made possible using this backup of association_properties.

[CLAassistant]

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