Replace nanoTime calls with a common routine

[prensing]

nanoTime() returns integer nanoseconds, which is not directly useful. Make a common call to scale that to floating seconds and replace uses through the code.

System.nanoTime() / 1_000_000_000.0

[prensing]

BTW for reference, "1_000_000_000.0" is not a good way to write that number. Use "engineering notation": 1.0e9. It is short, compact, and easy to read.

Also, floating division is the slowest of the simple arithmetic operations, by a fair bit. So, it is faster (and certainly no slower) to write:
1.0e-9 * System.nanoTime()
Note the minus sign in "1.0e-9". Of course, this statement is not used much in the robot code, and pretty hard to measure an actual difference. I mention it for "academic" interest.