What does this PR do?

When a resource name (for example, a DynamoDB table) resolves to an empty string, we skip emitting that tag. This prevents empty‐value overrides and lets Datadog correctly apply its inferred‐service precedence—peer.aws.dynamodb.table > peer.hostname > peer.db.system—without being short‐circuited by blank tags

Motivation

Fixes #3096

Reviewer's Checklist

• Changed code has unit tests for its functionality at or near 100% coverage.
• System-Tests covering this feature have been added and enabled with the va.b.c-dev version tag.
• There is a benchmark for any new code, or changes to existing code.
• If this interacts with the agent in a new way, a system test has been added.
• New code is free of linting errors. You can check this by running golangci-lint run locally.
• Add an appropriate team label so this PR gets put in the right place for the release notes.
• Non-trivial go.mod changes, e.g. adding new modules, are reviewed by @DataDog/dd-trace-go-guild.