[iis] adds iis_host tag to metrics

[ian28223]

What does this PR do?

PR adds iis_host tags to the metrics.

Motivation

If there are multiple instance configured, there's no distinction whether a metric came from which instance.

instances:
 - host: "."
 - host: "RemoteIISServer"
   username: "RemoteIISServer\user"
   password: "secret"

Additional Notes

• If the host is either "." or "localhost", the agent's hostname will be used as the iis_host instead

Review checklist (to be filled by reviewers)

• PR title must be written as a CHANGELOG entry (see why)
• Files changes must correspond to the primary purpose of the PR as described in the title (small unrelated changes should have their own PR)
• PR must have changelog/ and integration/ labels attached
• Feature or bugfix must have tests
• Git history must be clean
• If PR adds a configuration option, it must be added to the configuration file.

[ian28223]

will create tests but don't have ddev set up on windows so will rely on github for now

[codecov]

Codecov Report

Merging #3294 into master will increase coverage by 4.55%.
The diff coverage is 100%.

@@            Coverage Diff            @@
##           master   #3294      +/-   ##
=========================================
+ Coverage   85.44%     90%   +4.55%     
=========================================
  Files         676       6     -670     
  Lines       35517     150   -35367     
  Branches     4205      25    -4180     
=========================================
- Hits        30348     135   -30213     
+ Misses       4016      12    -4004     
+ Partials     1153       3    -1150

[gzussa]

Thanks for adding tests! 💯

[gzussa]

LGTM. Thanks 👍