[BUG] [Segment Replication] Rejected_requests are not reported correctly by _cat/segment_replication API

[Rishikesh1159]

Describe the bug
The rejected_requests column of _cat/segment_replication API is not reporting accurate metrics. The value of rejected_requests is always being 0 even though segment replication backpressure is triggered and rejecting requests

curl -X GET "localhost:9200/_cat/segment_replication?v"
shardId    target_node target_host checkpoints_behind bytes_behind current_lag last_completed_lag rejected_requests
[test6][0] runTask-0   127.0.0.1   0                  0b           0s          10ms               0

To Reproduce
Steps to reproduce the behavior:
-> Index documents into cluster continuously until Segment Replication backpressure mechanism is triggered.
-> Call the GET "_cat/segment_replication" API and check for the rejected_requests count per shard.
-> The value of rejected_requests is always being 0 and not getting updated.

Expected behavior
As Segment Replication backpressure mechanism is triggered and index requests are rejected, we should update the rejected_requests value in the _cat/segment_replication API.

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Host/Environment (please complete the following information):

• OS: [e.g. iOS]
• Version [e.g. 22]

Additional context
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