sdk: consolidate attribute normalization in attrnorm

[pellared]

Fixes #8499

Motivation

• Attribute normalization was split between module-local Trace and Logs truncation implementations and generated attrdedup packages used by Trace, Logs, and Metrics. This change establishes module-local internal/attrnorm packages generated from shared templates.
• This prepares for, but does not implement, the allocation and traversal optimizations proposed in Optimize truncation in Trace and Logs SDK #8491 as well as the attribute value depth limit prototyped in [Prototype] sdk: limit depth of nested attribute values #8534. It deliberately preserves the existing traversal, rebuilding, deduplication, truncation, concurrency, and public API behavior.

Changes

• Move the existing shared deduplication implementation and tests from internal/shared/attrdedup to internal/shared/attrnorm without changing its behavior.
• Move the equivalent Trace and Logs truncation implementations and tests into shared attrnorm templates.
• Generate deduplication and truncation for go.opentelemetry.io/otel/sdk and go.opentelemetry.io/otel/sdk/log; generate deduplication only for go.opentelemetry.io/otel/sdk/metric.
• Preserve the two existing hot-path integration shapes: Trace truncates a complete attribute.KeyValue, while Logs truncates its attribute.Value and keeps body handling deduplication-only.
• Update Trace, Logs, Metrics, and Resource consumers to import their own module-local internal/attrnorm package, and remove all obsolete attrdedup generation and consumers.
• Generate the shared truncation regression tests in both consuming modules, including direct TruncateValue coverage for negative limits, scalar strings, truncated map values, and unchanged maps, while retaining module-level integration coverage.
• Leave the changelog unchanged because this is an internal, behavior-preserving refactor.

Benchmarks

Focused before/after benchmarks were collected with -benchmem and 10 samples, then compared with benchstat.

• Trace truncation and span-limit paths: allocations and bytes/op are unchanged; timings are mixed with no consistent material regression.
• Logs truncation paths: allocations and bytes/op are unchanged. After retaining the original value-level call shape, affected ValueLimit paths are stable or faster (AddAttributes: -7.8%
  hit, -4.2% not-hit; SetAttributes: no significant change).
• Deduplication: the allocation-free fast path is stable (161.5 ns to 161.3 ns, no significant change), with unchanged allocations and bytes/op for all cases.
• Metric attribute paths: allocation counts are unchanged; timings are noisy and mixed despite the deduplication implementation being a rename-only move.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 84.0%. Comparing base (0f58da7) to head (28a2813).

Additional details and impacted files

@@          Coverage Diff          @@
##            main   #8611   +/-   ##
=====================================
  Coverage   84.0%   84.0%           
=====================================
  Files        326     328    +2     
  Lines      25942   25979   +37     
=====================================
+ Hits       21799   21838   +39     
+ Misses      3761    3760    -1     
+ Partials     382     381    -1     

Files with missing lines	Coverage Δ
sdk/internal/attrnorm/dedup.go	100.0% <ø> (ø)
sdk/internal/attrnorm/truncate.go	100.0% <100.0%> (ø)
sdk/log/internal/attrnorm/dedup.go	100.0% <ø> (ø)
sdk/log/internal/attrnorm/truncate.go	100.0% <100.0%> (ø)
sdk/log/provider.go	97.8% <100.0%> (ø)
sdk/log/record.go	100.0% <100.0%> (ø)
sdk/metric/instrument.go	98.1% <100.0%> (ø)
sdk/metric/internal/attrnorm/dedup.go	100.0% <ø> (ø)
sdk/metric/provider.go	100.0% <100.0%> (ø)
sdk/resource/resource.go	86.7% <100.0%> (ø)
... and 2 more

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[pellared]

@ps-mir, PTAL

[ps-mir]

I'm more satisfied with this change compared to initial plans. Despite the size of the PR, its a simplified refactoring, which moves truncation logic in shared internal template package and repurpose it as attrnorm.

Keeping truncation logic in a separate file is good.

There are no logical path changes apart from 1 small conditional logic as a result of unifying value truncation.

A nit on package comment, but nothing blocking. LGTM