getAttribute fetches data from http://metadata.google.internal/computeMetadata/v1/ without a timeout

[olavloite]

detectSupportedPlatform tries to fetch data from a URL. This can take a long time on hosts that do not have access to that host:

1. detectSupportedPlatform calls isRunningOnGcp():

   opentelemetry-operations-java/detectors/resources-support/src/main/java/com/google/cloud/opentelemetry/detection/GCPPlatformDetector.java

   Line 45 in ee8c192

   if (!isRunningOnGcp()) {

2. isRunningOnGcp() calls GcpMetadataConfig#getProjectId()
3. GcpMetadataConfig#getProjectId() calls getAttribute(String)
4. getAttribute tries to fetch data from http://metadata.google.internal/computeMetadata/v1/

The latter can potentially block for a long time. Would it maybe be better to add a timeout to that call?

Background: googleapis/java-spanner-jdbc#2250