fix(keep-alive): cache what is really needed not the whole VNode…

[zrh122]

cache what is really needed not the whole VNode data. it also fixes #9842
Fixes #2549
Fixes #9972

What kind of change does this PR introduce? (check at least one)

• Bugfix
• Feature
• Code style update
• Refactor
• Build-related changes
• Other, please describe:

Does this PR introduce a breaking change? (check one)

• Yes
• No

If yes, please describe the impact and migration path for existing applications:

The PR fulfills these requirements:

• It's submitted to the dev branch for v2.x (or to a previous version branch), not the master branch
• When resolving a specific issue, it's referenced in the PR's title (e.g. fix #xxx[,#xxx], where "xxx" is the issue number)
• All tests are passing: https://github.com/vuejs/vue/blob/dev/.github/CONTRIBUTING.md#development-setup
• New/updated tests are included

If adding a new feature, the PR's description includes:

• A convincing reason for adding this feature (to avoid wasting your time, it's best to open a suggestion issue first and wait for approval before working on it)

Other information:

[kadet1090]

Any update on when we can expect this PR to be merged?

[pcm0nk]

Can we have an update when this going to be merged? shouldnt this be high priority as it makes the app not usable after some time working and navigating. Also keep-alive has impact on page load. If this gets merged or at least a workaround is provided ( not removing keep-alive) would be nice.

[dyu]

I just noticed this bug too. The kept-alive node is not being destroyed. This is such a critical bug for a core component that's used by many

[chencmgithub]

Any update on when we can expect this PR to be merged?

which version had fixed the bug ??

[RichieChoo]

Any news?

[posva]

@zrh122 Thanks a lot for this! I reopened a new one with a refactor to avoid creating a new function on every render: #12015