feat: add file exporter implementation (#5207)

* commit

* finish added file exporters

* update license headers

* add changelog fragment

* add test tox environments

* commit

* simplify tests

* test improvements

* fix lint errors

* apply suggstions from ocelotl

* update dependencies

* update package version

* update exporter to write one line for each batch of telemetry

* introduce generic FileExporter class to reduce code duplication

* tweak generic FileExporter class

* add 'force_flush' method to log exporter

* move temporality and aggregation helper functions to json common package

* update documentation for file exporter

* fix docs build error

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Co-authored-by: Leighton Chen <lechen@microsoft.com>