Add Yezzey submodule to gpcontrib (#1752)

Yezzey is an open-source extension for Apache Cloudberry and
Greenplum 6 that transparently offloads Append-Only (AO/AOCO)
table data to S3-compatible object storage. Inspired by Snowflake
and AnyBlob, it extends the storage manager (smgr) so reads and
writes go to S3 instead of local disk, keeping the user interface
unchanged. A companion YProxy service acts as an I/O scheduler,
managing connection pooling and request prioritization to prevent
S3 throttling. Data is PGP-encrypted during upload. Benchmarks
show only 10–43% query slowdown versus local storage, far
outperforming PXF, making it ideal for cost-effective cold-data
tiering.

The main feature of Yezzey - you don't need to change tables or code;
just launch yezzey_define_offload_policy and move the data to S3.
In this way, you can unload your cluster using the available disk space.

Currently, it is widely used on Greenplum 6 instances, and the goal is
to provide users with the same interface in Cloudberry, so they can
seamlessly migrate to Cloudberry.

We placed Yezzey as a submodule, as we believe one day we will replace
all outdated solutions like AO/AOCO/Yezzey with PAX. However, that has
not happened yet and we still need Yezzey.

Co-authored-by: reshke <reshkekirill@gmail.com>

Author: leborchuk

.github/workflows/yezzey-ci.yaml

@@ -15,3 +15,6 @@
 	path = dependency/yyjson
 	url = https://github.com/ibireme/yyjson.git
 
+[submodule "gpcontrib/yezzey"]
+	path = gpcontrib/yezzey
+	url = https://github.com/open-gpdb/yezzey.git

.gitmodules

@@ -338,6 +338,12 @@ Apache Cloudberry includes codes from
 
       see licenses/LICENSE-citusdata.txt
 
+----------------------------
+   PostgreSQL License
+
+      gpcontrib/yezzey/*
+      see licenses/LICENSE-yezzey.txt
+
 ----------------------------
    Apache License - Version 2.0