Allow the parsing of UTF-16 configuration files

[Trovalo]

Feature Request

Allow the parsing of UTF-16 LE configuration files and UTF-16 in general
Why? because that's the default encoding used by Windows 10 (UTF-16 LE)
The files created by Telegraf itself will be in UTF-16
if I use the following PowerShell command and then I try to open the generated file I will get the error
.\telegraf.exe --input-filter win_perf_counters --output-filter influxdb config > myConf.conf

Is this urgent? no, it's not, you just need to open the file and save it UTF-8.

just for reference, I've got this small problem with:

• Win 10 Pro v1903 (but also the previous win version)
• Windows Server 2019 Standard v 1803

Proposal:

Change the parser so it can support UTF-16 encodings

Current behavior:

When trying to parse a .conf file wich is not in UTF-8 you get an error
Error running agent: Error parsing .<myFileName>.conf, line 1: invalid TOML syntax

Desired behavior:

telegraf can parse UTF-16 encoded files

Use case:

Every recent Windows machine will be able to open the Telegraf generated .conf file without checking if the file has the correct encoding

[danielnelson]

related #4880

[garciaolais]

Hi @Trovalo

In old PowerShell version I use the cmdlet Out-File instead of redirect >
In new PowerShell version I use redirect >