Enable compiled endpoint rules for all services and fix regionId parameter mismatch bug

[S-Saranya1]

Motivation and Context

Compiled endpoint rules generate endpoint resolution logic as direct Java code at codegen time, rather than interpreting rules at runtime. This provides ~40% better performance. The feature was behind a flag (enableGenerateCompiledEndpointRules) and already enabled for 344 services externally. This PR enables it for all remaining internal services by flipping the flag to true.

However, simply flipping the flag exposed a bug in the compiled endpoint provider codegen. The resolveEndpoint method extracts the region as a local String variable and always passes it to the root rule method:

Region region = params.region();
String regionId = region == null ? null : region.id();
RuleResult result = endpointRule0(params, regionId);  // always 2 args

But the root rule method's signature is generated based on scope analysis, it only includes regionId as a parameter if that method directly uses it. For most services, the root rule directly uses region (e.g., to look up the partition), so the 2-arg call matches:

private static RuleResult endpointRule0(Params params, String regionId) { ... } // 2 params - works

But for some services, the root rule just delegates to a child rule without using region itself:

private static RuleResult endpointRule0(Params params) { ... } // 1 param - compile error!

This creates a mismatch: the call site passes 2 arguments but the method only accepts 1.

This PR fixes the bug by adding a regionId() method to the endpoint params class that returns the region as a String (null-safe). The codegen now emits params.regionId() wherever the rules need the region as a string, eliminating the local variable and the parameter passing mismatch entirely.

Modifications

• CustomizationConfig.java — Flip enableGenerateCompiledEndpointRules default from false to true
• EndpointProviderSpec2.java — Remove region local variable extraction (Region region = params.region(); String regionId = ...) from resolveEndpointMethod(). Update initSymbolTable() to mark region params via addRegionParam() instead of creating a local
• SymbolTable.java — Replace String regionParamName with Set<String> regionParams. Add isRegionParam() and addRegionParam() methods
• CodegenExpressionBuidler.java — Remove regionParamName() accessor
• RenameForCodegenVisitor.java — When the referenced param is a region param, emit params.regionId() (append "Id" to accessor name) instead of params.region()
• EndpointParametersClassSpec.java — Generate regionId() method for Region-typed params: return region == null ? null : region.id()
• AuthSchemeParamsSpec.java — Add regionId() default method to the interface
• DefaultAuthSchemeParamsSpec.java — Add regionId() override
• EndpointRulesSpecUtils.java — Add directory fallback to rulesEngineResourceFiles2() so compiled rules codegen works when running from exploded classes in test environments

Testing

• All existing tests pass
• Golden file tests updated to verify generated code uses params.regionId() pattern
• Added runtime tests for regionId() (null and non-null cases)
• Dry-run build to live on build.amazon.com passed for AwsJavaSdk-Codegen

Screenshots (if appropriate)

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)

Checklist

• I have read the CONTRIBUTING document
• Local run of mvn install succeeds
• My code follows the code style of this project
• My change requires a change to the Javadoc documentation
• I have updated the Javadoc documentation accordingly
• I have added tests to cover my changes
• All new and existing tests passed
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• My change is to implement 1.11 parity feature and I have updated LaunchChangelog

License

• I confirm that this pull request can be released under the Apache 2 license