[YSQL] No results are returned for yb_lock_status() when UPDATE lock is waiting for another lock

[Karvy-yb]

Jira Link: DB-7189

Description

Steps to repro:

1. Create universe with enable_wait_queues, enable_deadlock_detection and enable_pg_locks flags. (Created on custom build)
2. Create database
3. Connect to database
4. create table tb(k int primary key, v int);
5. insert into tb values (1,1), (2,2);
6. txn_1: begin; select * from tb where k=1 for update;
7. On 2nd session: select * from yb_lock_status();
8. Notice that results are returned
9. On another session: update tb set v=11 where k=1; (This will wait for txn_1)
10. On 2nd session: select * from yb_lock_status();
11. Notice that no rows are returned

The issue is only observed when UPDATE lock is waiting for another lock (be it in fastpath or begin/commit transaction)

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[basavaraj29]

Tested it latest master + get lock status patch. I can see an error being returned.

yugabyte=# select * from yb_lock_status(null, null);
ERROR:  While decoding SubDocKey "G\x12\x10H\x80\x00\x00\x01!!J\x80!": Cannot decode value type kGroupEnd from the key encoding format: "!"

there seems to be an issue while decoding a few lock types at the wait-queue level. will look into it.