Excluding some attribute from allocation filter overrides the existing exclusion attributes

[jainankitk]

Describe the bug
Excluding some attribute from allocation filter overrides the existing exclusion attributes. Same is the case for include/require as FilterAllocationDecider recreates the filters from the difference passed to settings update consumer

To Reproduce
Steps to reproduce the behavior:
Exclude an ip from cluster settings:

curl -H "Content-Type: application/json" -XPUT localhost:9200/_cluster/settings -d '{
    "transient" : {
        "cluster.routing.allocation.exclude._ip" : "10.212.1.19"
    }
}'

Exclude another attribute say zone:

curl -H "Content-Type: application/json" -XPUT localhost:9200/_cluster/settings -d '{
    "transient" : {
        "cluster.routing.allocation.exclude.zone" : "us-west-2a"
    }
}'

Even though cluster setting shows both ip and zone, only zone filtering is honored as it was applied later

Expected behavior
For the reproduced behavior, both zone and ip exclusion should have been honored

Host/Environment (please complete the following information):

• Impacts all Opensearch versions