ViewMetadataBuilder does not always retain changes in current build

[c-thiel]

Apache Iceberg version

main (development)

Query engine

None

Please describe the bug 🐞

There is one edge case we missed in #12067 that might lead to a ViewVersion, added in the current build, not beeing retained:

1. Add view version 1 and set current
2. Set retention of versions to 2
3. Add view versions 2 & 3
4. Build

The builder should keep all versions (1, 2, 3) because 1 is the current version and must always be retained and neither 2 nor 3 may be discarded as they where added in this build.

A second build should retain 1 (current version) and 3 (highest id of the remaining) and discard 2.

As discussed CC @nastra

Willingness to contribute

• I can contribute a fix for this bug independently
• I would be willing to contribute a fix for this bug with guidance from the Iceberg community
• I cannot contribute a fix for this bug at this time