Make the number of task event loop configurable

[shangm2]

Description

1. This pr makes the number of task event loop within the group configurable via the configuration file

Motivation and Context

1. We saw event loop can get blocked while the underlying http connections are also being blocked
2. This pr makes the number of event loop configurable to reduce the chance of getting blocked while still uses the number of cores as default value

Impact

Test Plan

1. Deployed in pnb2_verifier_t1_1 with a configuration value of 500 for query replay
2. Confirm the config is updated

4. Confirm 500 task event loop are being used in coordinator

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Release Notes

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== RELEASE NOTES ==

General Changes
* Make the number of task event loop configurable via a configuration file