Bug: [FIX] add a configuration validation for workers



We don't have a validation check 
[number of workers in our config](https://github.com/juspay/hyperswitch/blob/94cd7b689758a71e13a3eaa655335e658d13afc8/crates/router/src/configs/settings.rs#L422) . But if the number of workers is zero actix straight out panics. Ref: https://docs.rs/actix-web/latest/actix_web/struct.HttpServer.html#method.workers
diff --git a/crates/router/src/configs/validations.rs b/crates/router/src/configs/validations.rs
index 910ae754347..69d0274d704 100644
--- a/crates/router/src/configs/validations.rs
+++ b/crates/router/src/configs/validations.rs
@@ -68,10 +68,18 @@ impl super::settings::Locker {
 
 impl super::settings::Server {
     pub fn validate(&self) -> Result<(), ApplicationError> {
-        common_utils::fp_utils::when(self.host.is_default_or_empty(), || {
+        use common_utils::fp_utils::when;
+
+        when(self.host.is_default_or_empty(), || {
             Err(ApplicationError::InvalidConfigurationValueError(
                 "server host must not be empty".into(),
             ))
+        })?;
+
+        when(self.workers == 0, || {
+            Err(ApplicationError::InvalidConfigurationValueError(
+                "number of workers must be greater than 0".into(),
+            ))
         })
     }
 }

## Type of Change
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- [x] Bugfix
- [ ] New feature
- [ ] Enhancement
- [ ] Refactoring
- [ ] Dependency updates
- [ ] Documentation
- [ ] CI/CD

## Description
<!-- Describe your changes in detail -->
Added validation check on number workers


### Additional Changes

- [ ] This PR modifies the API contract
- [ ] This PR modifies the database schema
- [ ] This PR modifies application configuration/environment variables

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2. `crates/router/src/configs`
3. `loadtest/config`
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## Motivation and Context
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It fixes #3510 

## How did you test it?
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Nothing to test in this PR

## Checklist
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- [ ] I formatted the code `cargo +nightly fmt --all`
- [ ] I addressed lints thrown by `cargo clippy`
- [ ] I reviewed the submitted code
- [ ] I added unit tests for my changes where possible
- [ ] I added a [CHANGELOG](/CHANGELOG.md) entry if applicable
