intel_powerstat not working if deployed within a container

Hello,

## TL;DR:
`intel_powerstat` does not work if Telegraf is deployed in a container.
I am referring to this ticket https://github.com/influxdata/telegraf/issues/14881.

---
### Relevant telegraf.conf

Relevant telegraf.conf

```toml
[[inputs.intel_powerstat]]
interval = "10s"
## The user can choose which package metrics are monitored by the plugin with
## the package_metrics setting:
## - The default, will collect "current_power_consumption",
## "current_dram_power_consumption" and "thermal_design_power"
## - Leaving this setting empty means no package metrics will be collected
## - Finally, a user can specify individual metrics to capture from the
## supported options list
## Supported options:
## "current_power_consumption", "current_dram_power_consumption",
## "thermal_design_power", "max_turbo_frequency", "uncore_frequency",
## "cpu_base_frequency"
package_metrics = ["current_power_consumption", "current_dram_power_consumption"]

## The user can choose which per-CPU metrics are monitored by the plugin in
## cpu_metrics array.
## Empty or missing array means no per-CPU specific metrics will be collected
## by the plugin.
## Supported options:
## "cpu_frequency", "cpu_c0_state_residency", "cpu_c1_state_residency",
## "cpu_c6_state_residency", "cpu_busy_cycles", "cpu_temperature",
## "cpu_busy_frequency"
## ATTENTION: cpu_busy_cycles is DEPRECATED - use cpu_c0_state_residency
cpu_metrics = ["cpu_frequency", "cpu_c0_state_residency", "cpu_c1_state_residency","cpu_c6_state_residency", "cpu_busy_frequency"]
```

### Logs from Telegraf

Telegraf logs

```text
2024-02-22T15:53:22Z I! Loading config: /etc/telegraf/telegraf.conf

2024-02-22T15:53:22Z I! Starting Telegraf 1.29.5 brought to you by InfluxData the makers of InfluxDB

2024-02-22T15:53:22Z I! Available plugins: 241 inputs, 9 aggregators, 30 processors, 24 parsers, 60 outputs, 6 secret-stores

2024-02-22T15:53:22Z I! Loaded inputs: intel_powerstat mqtt_consumer

2024-02-22T15:53:22Z I! Loaded aggregators:

2024-02-22T15:53:22Z I! Loaded processors:

2024-02-22T15:53:22Z I! Loaded secretstores:

2024-02-22T15:53:22Z I! Loaded outputs: influxdb_v2

2024-02-22T15:53:22Z I! Tags enabled: host=233d22a54fc0

2024-02-22T15:53:22Z I! [agent] Config: Interval:10s, Quiet:false, Hostname:"233d22a54fc0", Flush Interval:10s

2024-02-22T15:53:52Z I! [inputs.mqtt_consumer] Connected [tcp://mqtt.my.family:1883]

2024-02-22T15:53:52Z W! [inputs.intel_powerstat] Plugin started with errors: PowerTelemetry instance initialized with errors: failed to initialize msr: invalid MSR base path "/dev/cpu": file "/dev/cpu" does not exist; failed to initialize rapl: invalid base path of rapl control zone: file "/sys/devices/virtual/powercap/intel-rapl" does not exist

2024-02-22T15:54:00Z E! [inputs.intel_powerstat] Error in plugin: failed to update MSR time-related metrics: module "msr" is not initialized

2024-02-22T15:54:00Z E! [inputs.intel_powerstat] Error in plugin: failed to get "current_power_consumption": module "rapl" is not initialized

2024-02-22T15:54:00Z E! [inputs.intel_powerstat] Error in plugin: failed to get "current_dram_power_consumption": module "rapl" is not initialized
```

### System info

Ubuntu 22.04.03, Telegraf 1.29.5, Docker (Server Version) 25.0.3

### Docker

docker-compose.yml

```yaml
version: '3'

services:
telegraf:
image: telegraf:latest
container_name: telegraf
restart: unless-stopped
environment:
INFLUX_TOKEN: ""
HOST_ETC: "/hostfs/etc"
HOST_PROC: "/hostfs/proc"
HOST_SYS: "/hostfs/sys"
HOST_VAR: "/hostfs/var"
HOST_RUN: "/hostfs/run"
HOST_MOUNT_PREFIX: "/hostfs"
volumes:
- '/telegraf.conf:/etc/telegraf/telegraf.conf'
- '/:/hostfs:ro'
# depends_on:
# - influxdb
networks:
- services-network

networks:
services-network:
external: true
```

### Steps to reproduce

1. Ensure your system supports Intel MSR and/or RAPL and that the appropriate kernel modules have been loaded (e.g. using `lsmod | grep rapl`).
2. Ensure your system has `cpuid` installed (`sudo apt-get install -y cpuid`)-
3. Set up a network (in my example it's called `services-network` and is a `bridge`-type network).
4. Create a `docker-compose.yaml` with just Telegraf - as mentioned in the docker part above.
5. Configure it to use `input.intel_powerstat`.
6. Run the `docker-compose.yaml` file.
7. Wait about 20 seconds.

### Expected behavior

I expect the plugin to look for `PowerTelemtry` inside `/hostfs/sys/...` or `/hostfs/dev/...` etc., to not throw any errors and ultimately grab the corresponding values.

### Actual behavior

As `2024-02-22T15:53:52Z W! [inputs.intel_powerstat] Plugin started with errors: PowerTelemetry instance initialized with errors: failed to initialize msr: invalid MSR base path "/dev/cpu": file "/dev/cpu" does not exist; failed to initialize rapl: invalid base path of rapl control zone: file "/sys/devices/virtual/powercap/intel-rapl" does not exist` states, the plug in does not find the corresponding folders.
`/hostfs/dev/cpu` and `/hostfs/sys/devices/virtual/powercap/intel-rapl" do indeed exist, but they seem to not be found.

### Additional info

I've checked out the project and tried looking around, but I cannot find where (if at all) `HOST_MOUNT_PREFIX` or any of the `HOST_*` environment variables would be used. They are used to some extent in other plugins it seems, but not in this one.

Edit: I also figured the following: when **installing Telegraf locally** - even though MSR and RAPL are available - I had to do a couple of things before I could use it locally, namely this:
```bash
sudo chmod -R a+r /sys/devices/virtual/powercap/
sudo setcap cap_sys_rawio=ep /usr/bin/telegraf
sudo systemctl restart telegraf
```
- see https://stackoverflow.com/questions/18661976/reading-dev-cpu-msr-from-userspace-operation-not-permitted for /dev/cpu/*/msr issues
- see https://github.com/influxdata/telegraf/pull/11035 for RAPL-related stuff.

After that, **Telegraf started working locally** and sending values to my InfluxDB in the container as I'd expect it to.

> In the containerized Telegraf instance though, even mounting to `/sys` and `/dev` directly (not `/hostfs/sys` and `/hostfs/dev`) and even using `privileged: true` and `user: "0:0"`, I could **not** get it to work.