[SPM] Deprecate support for Spanmetrics Processor naming convention

[yurishkuro]

Which problem is this PR solving?

• Part 1 of [deprecate] Remove support for OTEL spanmetrics processor #4736

Description of the changes

• Add deprecation notice to CLI flag
• Add log message when using span metrics processor notation

How was this change tested?

$ go run ./cmd/all-in-one help
      --prometheus.query.support-spanmetrics-connector            (deprecated, will be removed after 2024-01-01 or in release v1.53.0, whichever is later)  Controls whether the metrics queries should match the OpenTelemetry Collector's spanmetrics connector naming (when true) or spanmetrics processor naming (when false). (default true)

$ PROMETHEUS_QUERY_SUPPORT_SPANMETRICS_CONNECTOR=false METRICS_STORAGE_TYPE=prometheus go run ./cmd/all-in-one
2023/09/09 20:29:19 using Spanmetrics Processor's metrics naming conventions (deprecated, will be removed after 2024-01-01 or in release v1.53.0, whichever is later)

cc @albertteoh

[codecov]

Codecov Report

Patch coverage is 100.00% of modified lines.

Files Changed	Coverage
plugin/metrics/prometheus/options.go	100.00%

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[albertteoh]

Thanks!