[confmap] Store original string in confmap.Conf

[mx-psi]

Description

• Adds new expandedValue struct that holds the original string representation if available for values resolved from a provider.
• Removes any mention of expandedValue in the public API by adding a sanitize step before returning any Gets or ToStringMaps.
• Adds new decoding hook that checks if the target field is of string type and uses the string representation in that case.

Link to tracking issue

Fixes #10605, Fixes #10405, Fixes #10659

Testing

This changes the behavior in some cases, I update the test cases.

Documentation

ENV value	${ENV} before unification	${ENV} in v0.105.0 (also ${env:ENV} before unification)	Value after this PR
foo\nbar	foo\nbar	foo bar	foo\nbar
1111:1111:1111:1111:1111::	1111:1111:1111:1111:1111::	Error	1111:1111:1111:1111:1111::
"0123"	"0123"	0123	"0123"

[mx-psi]

I still need to think about some edge cases and add more tests, but the overall approach should be clear now and can be reviewed

[codecov]

Codecov Report

Attention: Patch coverage is 85.13514% with 11 lines in your changes missing coverage. Please review.

Project coverage is 92.35%. Comparing base (7d5b1ba) to head (589a45f).

Files	Patch %	Lines
confmap/expand.go	65.38%	7 Missing and 2 partials ⚠️
confmap/confmap.go	95.34%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #10618      +/-   ##
==========================================
- Coverage   92.38%   92.35%   -0.04%     
==========================================
  Files         403      403              
  Lines       18729    18796      +67     
==========================================
+ Hits        17303    17359      +56     
- Misses       1066     1074       +8     
- Partials      360      363       +3     

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[codeboten]

I think this approach makes sense to address the issue, there are some lint errors that need addressing

[TylerHelmuth]

I agree that this looks like the right approach to me as it lets users continue to set yaml via env vars but also use exact inline env var values in strings.

[mx-psi]

@MovieStoreGuy it would really help if you can try this one out and confirm that it fixes your issue in an environment as close as possible to the one where you found it

[mx-psi]

Final call for reviews, I want to merge this by Thursday EU morning cc @open-telemetry/collector-approvers