vSphere plugin failure causing telegraf service to fail

### Use Case

From: https://github.com/influxdata/telegraf/issues/3723#issuecomment-1400954017

> While we will not add a global config option to let any and all plugins to start on failure, we are more than happy to see a plugin-by-plugin options to allow connection failures on start. If there is another plugin you are interested in seeing this for, please open a new issue (assuming one does not already exist), requesting something similar.

Can we change the vSphere plugin so that Telegraf doesn't fail if a password becomes invalid / expires for a single vSphere host.

This was also raised [here](https://github.com/influxdata/telegraf/issues/7500) but closed in favor of a global option to prevent Telegraf failing but that was closed in favor of chaging each plugin, which didn't happen for vSphere.

### Expected behavior

Telegraf doesn't fail if a password expires for a single vSphere host

### Actual behavior

Telegraf fails if there's a password becomes invalid for a single vSphere host and then all monitoring is lost for devices being monitored by that agent.

`2026-02-11T17:55:35Z E! [telegraf] Error running agent: starting input inputs.vsphere: ServerFaultCode: Cannot complete login due to an incorrect user name or password.`

### Additional info

_No response_

No file or test is named. Start by locating the inputs.vsphere plugin and its startup error handling, then reproduce the invalid-password case for one vSphere host. Done means Telegraf continues running and monitoring other devices when that host cannot authenticate.

Written by the indexing model from the issue text.