Google: expose campaign budget (incl. explicitly_shared) and impression-share metrics without GAQL

Reading a campaign's current daily budget, whether that budget is shared, and its impression-share metrics currently requires GET /v1/ads/insights GAQL passthrough, which draws on the shared Google operations budget. These are not
exotic reporting needs — they are what you need to answer "is this campaign capped by its budget?", which is the single most common budget question a customer has.

Concretely we need, per campaign: campaign_budget.amount_micros, campaign_budget.explicitly_shared, campaign_budget.resource_name, metrics.search_impression_share, metrics.search_budget_lost_impression_share,
metrics.search_rank_lost_impression_share.

The explicitly_shared flag is a safety requirement, not a nicety. Your team's guidance is not to point budget writes at campaigns on a shared budget until the behaviour is confirmed. Right now the only way for us to know which
campaigns those are is a GAQL call on the quota we are trying to protect — so the safe path and the cheap path are in conflict.

Request: add these to the campaign response (GET /v1/ads/campaigns) or to GET /v1/ads/campaigns/{campaignId}/analytics.