Describe the bug
Running flank using fladle gives duplicated messages on output.

Details
Flank provides 3 different types of output style [single, multi, verbose]. --output-style=multi is default when flank is running more than one execution. It is using ANSI codes to overwrite multiple lines in output. Some consoles may not supports ANSI codes so it can results with duplicated messages. Also running flank through gradle may give same results.

To reproduce
Run fladle with max-test-shards > 1. It's important to have more than one shard. The expected result was pasted in issue Flank/flank#841.

Additional context

• --output-style=multi displays separated status for each shard execution in separated line, lines are updated over time. Similar to gradle output when running multiple tasks in parallel. Requires ANSI codes support.
• --output-style=single displays shortened status of all executions in single line. Similar to gcloud output when running with sharding. Should work on any console.

Possible solutions

• Add option output-style to fladle so users can specify which one they want.
• Add output-style=single to executions under the hood so all executions on fladle will display single output.