feat(KeepAlive): support matchBy + allow custom caching strategy

[HcySunYang]

Close: #2084

This PR allows KeepAlive to use the vnode.key as the matching name, but the component's name still has a higher priority, which can avoid introducing breaking changes

Writing RFC.....

Edit: RFC vuejs/rfcs#284

[posva]

I think this should go through an RFC first to explore the different possible APIs, e.g. we could also only match by key if another prop is passed by-key, or match-by, etc

[HcySunYang]

Agree, there is still an issue requesting the management of the cache, also this #1518

[snltty]

这个啥时候能用上呢

[hezhongfeng]

I don’t like Vue’s KeepAlive cache policy , So I want to create a component like KeepAlive.
But When I use my Component with transition，there is a error Uncaught TypeError: Cannot read property '_' of null.
This error is create by packages/runtime-core/src/componentSlots.ts initSlots.
Looking forward to this PR.

[yuanjinyong]

这个啥时候能用上呢

同问

[hezhongfeng]

Is there any progress?