[core] Allow disabling Azure SDK tracing spans on a per-request basis

[maorleger]

In order to provide more granular control over Azure SDK traces and to align with other languages we should provide an option to disable tracing per request.

The scenario here is:

• A customer has enabled OTel tracing via our plugin (opted-in to tracing globally)
• A customer wants to suppress a single operation's Azure SDK traces from being created

This may be due to duplicate spans (with an HTTP instrumentation or other plugin provided) or just to reduce noise.

Proposed API:

export interface OperationTracingOptions {
    tracingContext?: TracingContext;
    suppressTracing?: bool; // new
}

Name and type TBD, but the goal is to provide a knob to disable tracing for a given request