Duration not rounded if timing file is updated

[SamuelWei]

Today I added cypress-split to my Github Action. I works great, however I believe there is a small bug.

If the duration of tests change, the timings.json file is updated.
The only issue is, that the new duration is not a rounded value, but instead has a lot of decimal places.

In the CI run output the values are rounded.

The values where also rounded when the CI created the timings.json file on the first run.

[SamuelWei]

The reason for this can be found in: https://github.com/bahmutov/cypress-split/blob/main/src/timings.js#L117

Once the timing data is merged, the result is not rounded.

However there is a more basic issue, as mentioned in #309. Each worker should only export the timings for the files it has run.
Otherwise merging the timings by using an average is resulting in a false result.

[SamuelWei]

I assume these would be the steps required to fix this:

• Check if timing files exists
• If not, write all timings to output file -> End
• Filter old timings file to only the specs used in this run
• Else, compare timings using threshold against old timings file
• If unchanged -> write filtered timings file to output file -> End
• Else, overwrite the timings of the filtered timings file -> output file -> End

@OriR @tuanna45 what do you think?