Update SDK to be consumed by Element Call's CallViewModel

Update the public API to export the primitives and operators the call
model needs, and change `LocalMediaInputs` from observable flags to
immediate booleans with imperative setters. Add session timings, media
quality and capture settings as configuration options, and allow the
host to override the transport discovery with explicit URLs.

sdk/src/config.ts

@@ -24,7 +24,7 @@ export interface DelayedLeaveTimings {
   /** How long (in milliseconds) the homeserver waits before sending the delayed leave. */
   delay_ms: number;
   /** How often (in milliseconds) the client restarts the delayed leave. */
-  restart_ms: number;
+  restart_ms?: number;
   /** How long (in milliseconds) a restart may take before it counts as failed. */
   restart_timeout_ms?: number;
 }
@@ -45,12 +45,18 @@ export interface SessionTimings {
   /** The session size at which the media key stops being rotated. */
   keyRotationParticipantLimit?: number;
   delayedLeave: DelayedLeaveTimings;
+  /**
+   * The timings used where the SFU restarts the delayed leave on the
+   * client's behalf, which lets the client stop renewing it itself.
+   */
+  delegatedDelayedLeave: DelayedLeaveTimings;
 }
 
 export const defaultSessionTimings: SessionTimings = {
   syncDisconnectGracePeriodMs: 10_000,
   networkErrorRetryMs: 1_000,
   delayedLeave: { delay_ms: 18_000, restart_ms: 4_000 },
+  delegatedDelayedLeave: { delay_ms: 3_600_000, restart_ms: 300_000 },
 };
 
 /** Media quality settings a host may pass; everything is optional. */