keep alive instance management

[ubugeeei]

Hi, thank you for awesome JavaScript framework, I use it all the time !
I have some requests for the keep-alive feature in VueJs. They are meant to help develop more flexibility.

1. Get a list of cached Vue instances.
   👇 Imagination (naming and other details are tentative)

const keepAlive = useKeepAlive()
const keptInstances = keepAlive.getKeptInstances()

2. Clear(distroy) the cache of instances

keepAlive.clear(it => it.name.includes("XXX"))
keepAlive.clearAll()

3. Set the cache lifetime.

<template>
<MyComponent keep-alive :lifetime="300000" />
</template>

set some attrs for manage keep-alive lifetime.

In the above example, if 300000 milliseconds (5 minutes) have passed since the instance was created,
it will be deleted by the activated or deactivated hooks.