synthesize_gps() should add noise to points based on total magnitude of the "noise vector" rather than applying noise to the individual vector components

[opentraffic]

synthesize_gps() should add noise to points based on total magnitude of the "noise vector" rather than applying noise to the individual vector components

[mxndrwgrdnr]

Fix implemented in validator.py here

[mxndrwgrdnr]

The biggest change here is semantic, where "noise" is now meant to indicate "noise ceiling", i.e. accuracy, in the synthetic GPS generation process.