Fix StringEncoder javadoc Java version and Android condition

[thswlsqls]

Fixes #8709

Description

• The javadoc called UnsafeStringEncoder a "Java 8+" implementation, but createIfAvailable() needs the String.value (byte[]) and String.coder fields, which Java 8 does not have, so Java 8 always falls back. The inline comment on the coder lookup already says "this only exists in Java 9+".
• That wording came from VarHandle string encoder #7701 and was carried over unchanged when Fix StringEncoder javadoc implementation priority order #8621 reordered the same bullet.
• Separately, Avoid unsafe string encoder on Android #8637 added an Android (Dalvik) early return to createUnsafeEncoder(), but the bullet still listed only the Java version condition. Added it to the same sentence.
• Updated the matching wording in the UnsafeStringEncoder javadoc and the StringEncoderHolder log message.

Testing done

• Docs-only, test-exempt: javadoc and one non-asserted Level.FINE log message; no behavior or API change.
• ./gradlew :exporters:common:check passed — 70 tests (61 test, 8 testSenderProvider, 1 testWithoutUnsafe), 0 failures.
• No apidiff update: all touched classes are japicmp-excluded io.opentelemetry.exporter.internal.*.

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Waiting on reviewers · refreshed 2026-08-10 01:36 UTC

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[codecov]

Codecov Report

❌ Patch coverage is 0% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 91.65%. Comparing base (d948e13) to head (37dac01).

Files with missing lines	Patch %	Lines
...exporter/internal/marshal/StringEncoderHolder.java	0.00%	1 Missing ⚠️

❌ Your patch check has failed because the patch coverage (0.00%) is below the target coverage (80.00%). You can increase the patch coverage or adjust the target coverage.

Additional details and impacted files

@@            Coverage Diff            @@
##               main    #8711   +/-   ##
=========================================
  Coverage     91.65%   91.65%           
  Complexity    10352    10352           
=========================================
  Files          1003     1003           
  Lines         27210    27210           
  Branches       3199     3199           
=========================================
  Hits          24939    24939           
  Misses         1566     1566           
  Partials        705      705           

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