[service] fix: use ipv6-aware host and port concatenation function

[terakoya76]

Description

Fixing the bug: the latest version of otel-collector failed to start with ipv6 metrics endpoint service telemetry.

This problem began to occur after #9037 with the feature gate flag enabled was merged. This problem is probably an implementation omission because the enabled codepath, which was originally added by #7871, is marked as WIP.

You can reproduce the issue with the config and the environment variable (MY_POD_IP=::1).

service:
  telemetry:
    logs:
      encoding: json
    metrics:
      address: '[${env:MY_POD_IP}]:8888'

Link to tracking issue

Fixes #10011

Testing

Added unittests to ensure the collector service to work with ipv6 metrics endpoint service telemetry.

I wondered whether to add a network argument, which is used as switching flag, to the GetAvailableLocalAddress function or create a new dedicated function for IPv6.
Since the GetAvailableLocalAddress function is widely used and its usage is usually assumed to be for IPv4, I chose the latter, not wanting to add more arguments each time we call.

Documentation

[codecov]

Codecov Report

Attention: Patch coverage is 58.97436% with 16 lines in your changes missing coverage. Please review.

Project coverage is 92.34%. Comparing base (5309d60) to head (2141f8c).

Files	Patch %	Lines
internal/testutil/testutil.go	57.89%	14 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #10343      +/-   ##
==========================================
- Coverage   92.40%   92.34%   -0.06%     
==========================================
  Files         393      393              
  Lines       18588    18620      +32     
==========================================
+ Hits        17176    17195      +19     
- Misses       1057     1068      +11     
- Partials      355      357       +2     

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[terakoya76]

Is there anything else I have to do to get a review?

Note: I did not add a change log because I assumed that changes were made only to internal packages. If this is an incorrect understanding, please point it out.

[marcus-griep-simplisafe]

Tracking this, as without this fix, it's causing problems with being able to use an up-to-date OTel collector in some IPv6 applications.

[TylerHelmuth]

@terakoya76 sorry that I missed this PR. Everything looks good to me. Please add a bug_fix changelog entry.

[terakoya76]

@TylerHelmuth
Thanks. I added a change log entry.