Unable to get Metrics for individual Switch Cases after upgrading to 4.27.0

Description: After upgrading from Benthos 4.10.0 to 4.27.0, we are unable to get the metrics of each switch case individually. In version 4.10.0, metrics were obtained separately for each switch case, but in version 4.27.0, the metrics are not separated by switch cases.

To Reproduce:

Use the following configuration in Benthos 4.10.0:

input:
generate:
count: 0
mapping: |
  root.foo = 42
output:
switch:
cases:
  - check: true
    output:
      label: ""
      retry:
        output:
          fallback:
            - http_client:
                url: "address"
                verb: POST
                headers:
                  Content-Type: application/json
            - http_client:
                url: "address"
                verb: POST
                headers:
                  Content-Type: application/json
  - check: false
    output:
      label: ""
      retry:
        output:
          fallback:
            - http_client:
                url: "address"
                verb: POST
                headers:
                  Content-Type: application/json
            - http_client:
                url: "address"
                verb: POST
                headers:
                  Content-Type: application/json

Run the configuration in Benthos 4.10.0 and execute curl localhost:4195/metrics.
The metrics being output as root.output.switch.0.output.fallback.0.
Upgrade to Benthos 4.27.0.
Run the same configuration and execute curl localhost:4195/metrics.
Observe the metrics being output as root.output.switch.output.retry.output.fallback.0 without individual case differentiation.

Expected behavior:

Metrics should be separated by switch cases as in the previous version, for example:

root.output.switch.0.output.fallback.0
root.output.switch.1.output.fallback.0

redpanda-data / benthos

Unable to get Metrics for individual Switch Cases after upgrading to 4.27.0 #58