Detect GPT initial load configured through setConfig

[ChristianPavilonis]

Problem

Publishers can disable GPT initial loading with the modern googletag.setConfig({ disableInitialLoad: true }) API. Trusted Server currently detects only the legacy googletag.pubads().disableInitialLoad() method.

When the modern API is used, window.tsjs.gptInitialLoadDisabled remains unset. A TS-owned slot is registered with display(), but it is omitted from the follow-up refresh(), so GPT never emits the GAM request and reports a fetch count of zero.

Acceptance criteria

• Detect initial-load disabling through both GPT configuration APIs.
• Refresh a TS-owned slot after display() when initial loading is disabled.
• Avoid adding a second request when initial loading remains enabled.
• Cover the modern setConfig() path with regression tests.