Make gc-base, gc-iceberg classes Java 8 compatible

[ajantha-bhat]

GC modules can be used by engines to build its own distributed GC logic. Hence, it has to be java8 compatible.

[snazy]

TL;DR this is way too much, doing way more than necessary

[ajantha-bhat]

TL;DR this is way too much, doing way more than necessary

Goal was to make gc-base and gc-iceberg compatible with java 8.
So, I changed nessie-conventions-iceberg to use java 8 and then started fixing its dependencies compatibility.

May be you meant introduce a new profile nessie-conventions-iceberg8 and use for only gc-base and gc-iceberg and its dependencies. I will give it a try.

[ajantha-bhat]

TL;DR this is way too much, doing way more than necessary

Updated.