drpcpool: add support for ShouldRecord

[suj-krishnan]

Add a ShouldRecord func to drpcpool and dprcclient options to enable/disable pool metrics from cockroach.

[cthumuluru-crdb]

One minor comment. Otherwise looks good.

[Copilot]

Pull request overview

Adds a ShouldRecord callback to client connection and pool configuration to allow runtime control over whether metrics are recorded (intended for CockroachDB integration).

Changes:

• Replace CollectMetrics with ShouldRecord func() bool for client byte metrics recording.
• Add ShouldRecord func() bool to drpcpool.Options and gate pool metric updates behind it.
• Update and extend tests to reflect the new metric-recording controls.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
internal/integration/metrics_test.go	Updates integration tests to use ShouldRecord and validate the “not recorded when nil” behavior.
drpcpool/pool.go	Adds Options.ShouldRecord and gates pool metric initialization and updates behind it.
drpcpool/pool_test.go	Updates existing tests to set ShouldRecord, and adds coverage for ShouldRecord == false.
drpcmetrics/metrics.go	Extends metered transport wrapper to consult shouldRecord() per Read/Write.
drpcconn/conn.go	Replaces CollectMetrics with ShouldRecord and wires it into metered transport creation.
drpcclient/dialoptions.go	Adds WithShouldRecordFunc and passes the callback into drpcconn.Options.

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[Copilot]

ToMeteredTransport stores shouldRecord and Read/Write call it unconditionally; if a caller passes a nil shouldRecord this will panic at runtime. Consider defaulting shouldRecord to a func that always returns true (or false) when nil, and/or document/enforce that it must be non-nil.