`az ad sp create-for-rbac` should support finer grain of credential expiry time

**Related command**
`az ad sp create-for-rbac`

**Is your feature request related to a problem? Please describe.**
Currently, only integer `--years` is supported which is too rough:

```
> az ad sp create-for-rbac -h
...
Credential Arguments
--years : Number of years for which the credentials will be valid.
Default: 1 year.
```

The minimum expiry time is 1 year which is against the security best practice of setting expiry time as short as possible.

> [!CAUTION]
> **If there is a policy in the tenant that forbids expiry time >= 1 year, `az ad sp create-for-rbac` will fail.**

**Describe the solution you'd like**

1. Support `--end-date` similar to that from `az ad app credential reset` and `az ad app create`.
2. Support `--days` like Azure Portal: 

**Describe alternatives you've considered**
Drop `--year` as it encourages imprecise expiry time and it also causes ambiguity in leap years (https://github.com/Azure/azure-cli/issues/28520).