Fix: Return None for Over-Segmented IPv6 Addresses

[razeghi71]

This PR addresses an issue with the current implementation of the Ipv6Address.fromString method. Previously, an IPv6 address with too many segments would cause an exception instead of returning None. This PR introduces a fix to ensure that over-segmented IPv6 addresses correctly return None, aligning with the expected behavior of the method.

Changes:

• Added a condition to check for negative numCondensedZeroes, which indicates over-segmentation.
• Adjusted the logic to correctly handle the prefix and suffix of the IPv6 address during parsing.

Examples:

• Before the fix: For an input like 1:1:1:1:1:1:2:1:3, the Ipv6Address.fromString method would throw a java.lang.ArrayIndexOutOfBoundsException: Index 16 out of bounds for length 16.
• After the fix: The same input now returns None, indicating an invalid IPv6 address, as expected.
• Before the fix: For an input like ::1:1:1:1:1:1:2:1:3, the Ipv6Address.fromString method would throw a java.lang.ArrayIndexOutOfBoundsException: Index -2 out of bounds for length 16.
• After the fix: The same input now returns None, indicating an invalid IPv6 address, as expected.

[CLAassistant]

All committers have signed the CLA.

[mpilquist]

Thanks!