Add forceRefresh parameter to getAccessToken() for near-expiry token recovery

[jethibau-msft]

Problem

SDK.getAccessToken() has no way to request a fresh token from the host. The IAuthorizationTokenProvider interface in azure-devops-extension-api already defines forceRefresh?: boolean on getAuthorizationHeader(), but getAccessToken() never accepted or forwarded this parameter.

Fix

Add an optional forceRefresh parameter to getAccessToken() and forward it to the host via XDM:

// Before
export async function getAccessToken(): Promise<string> {
    return parentChannel.invokeRemoteMethod<{ token: string }>("getAccessToken", hostControlId)
        .then((tokenObj) => { return tokenObj.token; });
}

// After
export async function getAccessToken(forceRefresh?: boolean): Promise<string> {
    return parentChannel.invokeRemoteMethod<{ token: string }>("getAccessToken", hostControlId, [forceRefresh])
        .then((tokenObj) => { return tokenObj.token; });
}

This is a backwards-compatible change — existing callers with no arguments are unaffected. The host-side DevOps.HostControl handler would also need to honor the parameter for the full flow to work.

Companion PR

The azure-devops-extension-api also has two bugs (broken 401 retry + default auth provider ignoring forceRefresh): microsoft/azure-devops-extension-api#187

Impact

Every ADO web extension using SDK.getAccessToken() or getClient() is affected during long-running sessions when tokens approach expiry.

[jethibau-msft]

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