Deal with discarded tabs

[fregante]

Extracted from:

• Review how we deal with a large amount of tabs #5041
• Investigate delayed execution of bricks in resource-starved browsers #6581

Findings:

• messages sent to discarded tabs return the same error as when a tab doesn't exist or when runtime.onMessage wasn't called
• the Messenger does not retry this error if the tab does not exist
  • https://github.com/pixiebrix/webext-messenger/blob/0e4fbbd6670dc24ad248b5a22b89a3810bcee88f/source/sender.ts#L133
• the Messenger will retry this error if the tab was discarded

What we can do:

• Do not retry discarded tabs, return specific error webext-messenger#162
• #6624: Exclude discarded tabs in broadcasts and other "all tabs" actions #6626
  

  pixiebrix-extension/src/background/activeTab.ts

  Lines 6 to 8 in d6128c7

  	export async function getTabsWithAccess(): Promise<TabId[]> {
  	const { origins } = await browser.permissions.getAll();
  	const tabs = await browser.tabs.query({ url: origins });