Query Builder in InfluxDB UI doesn't show all existent tag keys in Group operation

__Steps to reproduce:__
List the minimal actions needed to reproduce the behavior.

1. Open the InfluxDB UI on Explore option
2. Browse a bucket
3. Select a metric
4. Select Group operation

__Expected behavior:__
I was expecting to see all available tags for the selected measurement in the selected bucket for the selected time interval.

__Actual behavior:__
UI shows only a few metrics, including only one or a few user tags .

__Environment info:__

* System info: Linux 5.4.0-1030-aws x86_64
* InfluxDB version: InfluxDB 2.1.1 (git: 657e1839de) build_date: 2021-11-09T03:03:48Z
* Other relevant environment details: AWS EC2 instance running Ubuntu Server, installation via .deb package.
* 4 vcpus, 16GB of RAM

__Config:__
```
INFLUXD_CONFIG_PATH=/etc/influxdb/config.toml
INFLUXD_BOLT_PATH=/var/lib/influxdb/influxd.bolt
INFLUXD_ENGINE_PATH=/var/lib/influxdb/engine
INFLUXD_STORAGE_WAL_FSYNC_DELAY=0s
INFLUXD_QUERY_CONCURRENCY=6
INFLUXD_QUERY_INITIAL_MEMORY_BYTES=10485760
INFLUXD_LOG_LEVEL=debug
INFLUXD_FLUX_LOG_ENABLED=true
INFLUXD_STORAGE_RETENTION_CHECK_INTERVAL=15m0s
GOGC=60
```

__Logs:__
N/A

__Performance:__
N/A

```sh
# Commands should be run when the bug is actively happening.
# Note: This command will run for ~30 seconds.
curl -o profiles.tar.gz "http://localhost:8086/debug/pprof/all?cpu=30s"
iostat -xd 1 30 > iostat.txt
# Attach the `profiles.tar.gz` and `iostat.txt` output files.
```
[iostat.txt](https://github.com/influxdata/influxdb/files/8255501/iostat.txt)
[profiles.tar.gz](https://github.com/influxdata/influxdb/files/8255502/profiles.tar.gz)

Tags available:

```
import "influxdata/influxdb/schema"
schema.tagKeys(bucket: "logs_consolidated", predicate: (r) => r._measurement == "errors_with_classes_1h", start: -1d)

Result:
_value:string
----------------------
_start
_stop
_field
_measurement
class
class_type
code
error_type
hostname
provider
reason
retry
srcip
subcode
```

Tags shown:

Start by reproducing the issue in the Explore Query Builder and compare the tags returned by the shown schema.tagKeys query with the tags offered by the Group operation. Done means all available tags for the selected measurement, bucket, and time interval appear in the UI.

Written by the indexing model from the issue text.