Fix unsatisfied dependency issue in leaderOnlyTokenCrawler

[bbenner7635]

Description

Crawler plugins are failing to startup due to autowiring setup:

2025-11-01T18:08:01.350 [main] ERROR org.opensearch.dataprepper.core.validation.LoggingPluginErrorsHandler - 1. pipeline.source.microsoft_office365: caused by: Error creating bean with name 'leaderOnlyTokenCrawler' defined in URL [jar:file:/opt/amazon/lib/source-crawler-2.x.893.jar!/org/opensearch/dataprepper/plugins/source/source_crawler/base/LeaderOnlyTokenCrawler.class]: Unsatisfied dependency expressed through constructor parameter 0; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type 'org.opensearch.dataprepper.plugins.source.source_crawler.base.LeaderOnlyTokenCrawlerClient' available: expected at least 1 bean which qualifies as autowire candidate. Dependency annotations: 
{}
 caused by: No qualifying bean of type 'org.opensearch.dataprepper.plugins.source.source_crawler.base.LeaderOnlyTokenCrawlerClient' available: expected at least 1 bean which qualifies as autowire candidate. Dependency annotations: 
{}

CrawlerSourcePlugin uses the packagesToScan annotation which includes CrawlerApplicationContextMarker.class. This likely causes Spring to scan and try to autowire beans like LeaderOnlyTokenCrawlerClient from the source_crawler package even when there is no bean instantiated

Casting as LeaderOnlyTokenCrawlerClient will prevent Spring from autowiring LeaderOnlyTokenCrawlerClient as a dependency of crawler plugins which do not require it

Issues Resolved

N/A

Check List

• New functionality includes testing.
• New functionality has a documentation issue. Please link to it in this PR.
  • New functionality has javadoc added
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