Greeting doesn't output as expected

Uncovered with https://github.com/snapcore/snapcraft/pull/3958

Snapcraft makes the two calls on startup:
```
emit.init(
mode=get_verbosity(), # verbosity comes from environmental variable
)

...

dispatcher.pre_parse_args(sys.argv[1:])
```
These two calls both call `craft_cli.set_mode()`. If the verbosity levels don't match between these two calls, then craft-cli may not log as expected. See scenarios below.

## Scenario 1

Greeting logged when in `quiet`.

### input
`SNAPCRAFT_VERBOSITY_LEVEL=trace snapcraft --verbosity=quiet`

### output
```
2022-10-26 11:26:15.135 Starting Snapcraft 7.2.1.post5+git529c27a2
2022-10-26 11:26:15.135 Logging execution to '/home/developer/.cache/snapcraft/log/snapcraft-20221026-112615.134692.log'
```
## Scenario 2

Greeting logged twice.

## input
`SNAPCRAFT_VERBOSITY_LEVEL=trace snapcraft --verbosity=trace`

### output
```
2022-10-26 11:25:57.052 Starting Snapcraft 7.2.1.post5+git529c27a2
2022-10-26 11:25:57.052 Logging execution to '/home/developer/.cache/snapcraft/log/snapcraft-20221026-112557.051720.log'
2022-10-26 11:25:57.052 Starting Snapcraft 7.2.1.post5+git529c27a2
2022-10-26 11:25:57.052 Logging execution to '/home/developer/.cache/snapcraft/log/snapcraft-20221026-112557.051720.log'
... (logs continue in trace-level)
```

Reproduce the two scenarios with SNAPCRAFT_VERBOSITY_LEVEL and the matching snapcraft --verbosity values. Trace emit.init(), dispatcher.pre_parse_args(sys.argv[1:]), and their calls to craft_cli.set_mode(). Done means quiet mode produces no greeting and trace mode produces the greeting once, without duplicate output.

Written by the indexing model from the issue text.