Tests

Rename `files_upload_external` to `files_upload_v2` (#536) #1372

Job	Run time
test (ruby=2.7)	39s
test (ruby=2.7, concurrency=async-websocket)	32s
test (ruby=3.0)	18s
test (ruby=3.1)	19s
test (ruby=3.2)	26s
test (ruby=3.3)	24s
test (ruby=ruby-head)	21s
test (ruby=jruby-head)	1m 53s
coveralls	2s
	4m 54s

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