Accept threadpool executors for FailsafePlugin through yaml configuration.

[rameshmalla]

The proposal is to support yaml based configuration to add threadpool exuectors to failsapfe plugin

Detailed Description

riptide spring boot starter by default, accepts most HTTP client configurations through YAML, making it simple and convenient to configure and quickly start using the Riptide client. For the FailsafePlugin, the current approach for introducing a custom thread pool executor involves configuring it via code instead of configuration.

While this approach offers greater control over thread pool management and allows for fine-tuning of execution threads, it requires additional code-based configuration as opposed to the more declarative YAML-based configuration used for other HTTP client settings.

The proposal is to introduce YAML based thread pool configuration for FailSafePlugin and re-use the existing thread pool construction logic in ripitde which supports opentracing and micrometer features out of the box.