Minor fault in influx v1 shell: Incompleteness in the help-as-you-type function

**Summary:**
The helping function that show you suggestions as you type lack vital suggestions for SHOW TAG.

**Info + how to reproduce:**
I run the latest version of influx CLI on a Debian 11 machine (package: influxdb2-cli 2.7.3-1).
```
# influx version
Influx CLI dev (git: none) build_date: 2023-04-28T14:24:14Z
```

I run the v1 shell and connect to my InfluxDB v2 (also latest version, on the same Debian 11 machine).
```
# influx v1 shell
InfluxQL Shell dev
Connected to InfluxDB OSS v2.7.5
> use Main
> precision rfc3339
```
Now I type `SHOW TAG ` at the prompt.
I'm presented with just one possible suggestion: `VALUES`.
It should also show suggestions for `KEY` and `KEYS`.

Also:
If you type `SHOW TAG VALUES` it should help you with the next word(s) `WITH KEY`.

Start by locating the v1 shell's help-as-you-type completion code and reproduce the reported SHOW TAG and SHOW TAG VALUES inputs. Done means the suggestions include KEY and KEYS after SHOW TAG, and WITH KEY for the subsequent SHOW TAG VALUES input.

Written by the indexing model from the issue text.