Automatic merge from submit-queue (batch tested with PRs 41530, 44814, 43620, 41985)

Fixes juju kubernetes master: 1. Get certs from a dead leader. 2. Append tokens.

**What this PR does / why we need it**:
Fixes two issues with the Juju kubernetes master.

1. Grab certificates from a leader that is already removed.
2. Append (not truncate) auth tokens 

**Which issue this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close that issue when PR gets merged)*: fixes #
fixes #43563 fixes #43519

**Special notes for your reviewer**:

**Release note**:

```
Recover certificates from leadership context in case all masters die in a Juju deployment
```