Inconsistency in required parameters for bucket commands

One bucket command can specify a bucket by name:
```
$ influx bucket delete --name test2
ID Name Retention Shard group duration Organization ID Schema Type Deleted
4336 test2 infinite n/a 26ca implicit true
```
And another cannot:
```
$ influx bucket update -r 3w --name test2
Error: Required flag "id" not set
```
It seems that if _delete_ can look up the bucket by name, then _update_ could as well.

Start by tracing the `influx bucket delete` and `influx bucket update` command definitions and their required-flag validation. Compare how delete resolves `--name` with update's `--id` requirement; done means update accepts a bucket name consistently and its existing behavior remains covered by tests.

Written by the indexing model from the issue text.