Improve remaining Javadoc in camel-api: grammar, method docs, and exception constructors

[gnodet]

Summary

Final batch of Javadoc improvements for the camel-api module, addressing all remaining issues from the analysis:

Grammar and typo fixes:

• RoutePolicyFactory: "automatic" -> "automatically" + added registration docs
• HeaderFilterStrategy: "plug-able" -> "pluggable", "filter header" -> "filter headers"
• StreamCachingStrategy: "aas" -> "as" (3x) + replaced tautological class doc
• ResumeAction: "and interface" -> "an interface"
• WritableHealthCheckRepository: fixed incorrect copy-paste class description
• CamelContext: fixed 6 "its" -> "it's" (contraction) occurrences

Undocumented API elements:

• TypeConverter.MISS_VALUE: added sentinel value description
• Experimental.revision(): added annotation element description

Method-level Javadoc added to 6 classes:

• PropertiesValidationResult (42 methods)
• VaultConfiguration (28 methods)
• HealthCheckResultBuilder (14 methods)
• ResumeStrategy (2 methods)
• BaseService (32 methods)
• RestConfiguration (65 methods)

Exception constructor @param tags:

• Added to 24 remaining exception classes (CamelException, ValidationException, RollbackExchangeException, ExpressionEvaluationException, etc.)

All changes are Javadoc-only — no functional code modified. 38 files changed, 384 insertions.

Test plan

• mvn install -pl core/camel-api -DskipTests passes
• Formatter applied (mvn formatter:format impsort:sort)
• No generated file changes needed

[github-actions]

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🧪 CI tested the following changed modules:

• core/camel-api

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