Hide LogRecord attributes Implementation Details from exporters

[lalitb]

Changes

Hide the implementation details of LogRecord attributes by:

• Making the LogRecord attributes private to the opentelemetry-sdk crate.
• Creating wrapper methods attributes_iter(), attributes_contains(), and attributes_len() to expose the functionality of these attributes to the exporter.

These changes will enable modifications to the internal implementation of these attributes without requiring any changes in the exporter code.

Merge requirement checklist

• CONTRIBUTING guidelines followed
• Unit tests added/updated (if applicable)
• Appropriate CHANGELOG.md files updated for non-trivial, user-facing changes
• Changes in public API reviewed (if applicable)

[cijothomas]

I think this is not required to be public. If an exporter needs it, then can write a helper function to get this by using the above 2 methods.

[cijothomas]

I think we need to offer API to modify an existing entry, remove an existing entry too. These are critical to ensure we allow redaction, enrichment capabilities. Lets track it as separate issue for adding in the future.

[codecov]

Codecov Report

Attention: Patch coverage is 84.93151% with 22 lines in your changes missing coverage. Please review.

Project coverage is 74.9%. Comparing base (9f71652) to head (a85cbaf).

Files	Patch %	Lines
opentelemetry-stdout/src/logs/transform.rs	0.0%	14 Missing ⚠️
opentelemetry-proto/src/transform/logs.rs	61.5%	5 Missing ⚠️
opentelemetry-sdk/src/logs/record.rs	83.3%	3 Missing ⚠️

Additional details and impacted files

@@          Coverage Diff          @@
##            main   #1985   +/-   ##
=====================================
  Coverage   74.8%   74.9%           
=====================================
  Files        122     122           
  Lines      20429   20473   +44     
=====================================
+ Hits       15299   15341   +42     
- Misses      5130    5132    +2     

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[cijothomas]

LGTM.
Its probably better not to expose len() method initially, not a blocker if we expose it as well.