EndpointUtil.validateEndpoint not handling all valid DNS host names

[jameyg42]

Describe the bug
the recent check to validate hostname in EndpointUtils.validateEndpoint() is hitting
https://bugs.openjdk.org/browse/JDK-8188305
that is, URI.getHost() returns null for hostnames that are valid according to modern DNS standards (in my particular case, hostnames w/ a segment that starts with a number).

Steps to reproduce
set otel.exporter.etlp.endpoint to http://otlp.1234-k8s-namespace:4318 (or any other value that triggers the URI.getHost() bug)

What did you expect to see?
normal agent startup

What did you see instead?

io.opentelemetry.sdk.autoconfigure.AutoConfiguredOpenTelemetrySdkBuilder - Error encountered during autoconfiguration. Closing partially configured components.
io.opentelemetry.sdk.autoconfigure.spi.ConfigurationException: Unexpected configuration error
        at io.opentelemetry.sdk.autoconfigure.AutoConfiguredOpenTelemetrySdkBuilder.buildImpl(AutoConfiguredOpenTelemetrySdkBuilder.java:510)
        at io.opentelemetry.sdk.autoconfigure.AutoConfiguredOpenTelemetrySdkBuilder.build(AutoConfiguredOpenTelemetrySdkBuilder.java:431)
...
Caused by: java.lang.IllegalArgumentException: Invalid endpoint, must start with http:// or https://: http://otlp-collector.14014-mosaik:4318/v1/metrics
        at io.opentelemetry.exporter.internal.EndpointUtil.validateEndpoint(EndpointUtil.java:34)
        at io.opentelemetry.exporter.otlp.internal.HttpExporterBuilder.setEndpoint(HttpExporterBuilder.java:94)
        at io.opentelemetry.exporter.otlp.http.metrics.OtlpHttpMetricExporterBuilder.setEndpoint(OtlpHttpMetricExporterBuilder.java:127)

What version and what artifacts are you using?
edot-java:1.12.0 (otel-instrumentation:2.30.0; sdk: 1.64.0)

possible workaround
in my particular case, because this was a hostname from a k8s namespace that follows a number-prefix naming convention, I was able to get around the java bug simply by using the service FQDN (otlp.1234-k8s-namespace.svc.cluster.local)