Partial for #31607

• Create new setPurpose action in the PromptUI, so that publishers can explicitly tell AMP which purposes shave been accepted and rejected
  • setPurpose accepts multiple args (purposes) and each must be set to True/False (denoting if the purpose has been consented to)

<button on="tap:ABC.setPurpose(purpose-foo=true)">ACCEPT FOO</button>
<button on="tap:ABC.setPurpose(purpose-foo=false,purpose-bar=true)">ACCEPT FOO & BAR</button>
<label for="consent-purpose-xyz">
  <input type="checkbox" on="change:ABC.setPurpose(purpose-xyz=event.checked)" id="consent-purpose-xyz" />
  Toggle Bar Consent
</label>

• The purposes will be stored in the consentStateManager, which will eventually store these values in local storage (to cache) and propagate them to the consent policy manager (to block and unblock).

• Modified the existing accept and reject actions in the PromptUI to accept a purposeConsentDefault argument that will tell AMP to use this value as a fallback for all purposes state in purposeConsentRequired.

<button on="tap:ABC.accept">Accept</button> 
<button on="tap:ABC.reject(purposeConsentDefault=accepted)">Reject</button>