Fix fractional JSON size limits

[codingkiddo]

Summary

Fix fractional size handling in JsonSizeConstraint.

The existing implementation rounds the numeric value before converting KB, MB, or GB values to bytes. As a result, fractional limits such as 0.5KB are interpreted incorrectly.

For example:

• Expected: 0.5KB = 512 bytes
• Previous behavior: round(0.5) * 1024 = 1024 bytes

Changes

• Preserve the fractional value until after conversion to bytes.
• Round the final byte count instead of the original numeric value.
• Add a regression test covering a 0.5KB limit.
• Correct the JsonSizeConstraint Javadoc examples to use quoted string values.

Testing

Ran:

./gradlew :maestro-common:test \
  --tests com.netflix.maestro.validations.JsonSizeConstraintTest

and:

./gradlew :maestro-common:check