[Feature] Support btree global index.

[ChaomingZhangCN]

Search before asking

• I searched in the issues and found nothing similar.

Motivation

Ref apache/paimon#6869

Solution

No response

Anything else?

No response

Are you willing to submit a PR?

• I'm willing to submit a PR!

[steFaiz]

👍

[ChaomingZhangCN]

[lxy-9602]

Thank you for this issue! We believe that BTree would be extremely helpful for range queries and fast random lookups on sortable data. Look forward to your contribution. Just a gentle note—if the corresponding index type is consistent with the Java implementation (as we expect it does), please ensure the compatibility with Java Paimon’s index format in read/write process.