[Default Read/Write Timeout 5/N] Rename rollout gate to AWS_ENABLE_DEFAULT_SOCKET_TIMEOUT_2026

[zoewangg]

Motivation and Context

This is series item 5/N of the default read/write timeout work. Earlier items introduced an interim, off-by-default rollout gate under the working name AWS_ENABLE_DEFAULT_READ_TIMEOUT_2026. The cross-SDK teams have since settled on SOCKET (rather than READ) as the name for this gate. It is a mechanical, behavior-preserving rename with no functional change.

Base branch is the feature branch for this series, not master.

Modifications

Renamed the rollout-gate symbols from the interim READ name to the settled SOCKET name.

• SdkSystemSetting: AWS_ENABLE_DEFAULT_READ_TIMEOUT_2026 -> AWS_ENABLE_DEFAULT_SOCKET_TIMEOUT_2026. This also renames the environment variable string AWS_ENABLE_DEFAULT_SOCKET_TIMEOUT_2026 and the system property aws.enableDefaultSocketTimeout2026 (formerly aws.enableDefaultReadTimeout2026), which are the customer-facing opt-in names for this interim gate.
• Resolver: EnableDefaultReadTimeout2026Resolver -> EnableDefaultSocketTimeout2026Resolver (class, file, and its builder method/field defaultEnableSocketTimeout2026). The test class/file was renamed to match.
• SdkClientOption: DEFAULT_ENABLE_READ_TIMEOUT_2026 -> DEFAULT_ENABLE_SOCKET_TIMEOUT_2026.
• codegen CustomizationConfig: field + getter/setter defaultEnableSocketTimeout2026, the BaseClientBuilderClass emission that reads it, and the affected customization/fixture resources.
• AwsDefaultClientBuilder (aws-core): updated all references to the renamed resolver and client option, plus the associated Javadoc {@code} references.

Testing

Built and ran the affected module tests. A repo-wide grep confirms no remaining references to any of the old names

Types of changes

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

This is a behavior-preserving rename/refactor; neither category above applies.

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
• I have added a changelog entry.
• 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