Refactor org.apache.http related packages to private packages

[nimsara66]

Purpose

Fixes: wso2/api-manager#3206

Approach

The current implementation imports the org.apache.http.impl.nio.* and org.apache.http.nio.* packages from the OSGi runtime:

<Import-Package>
    !com.google.gson.internal,
    io.opentelemetry.api.common.*,
    org.apache.http.impl.nio.*,
    org.apache.http.nio.*,
</Import-Package>

Additionally, it bundles the httpasyncclient as an embedded dependency.

This approach results in the following error:

java.lang.NoClassDefFoundError: org/apache/http/nio/client/HttpAsyncClient

The error occurs because the HttpAsyncClient class is not exported to the OSGi runtime, leading to missing class definitions at runtime.

This PR refactors the dependency management approach by moving the org.apache.http.impl.nio.* and org.apache.http.nio.* packages to private packages. This change ensures that these packages are no longer imported from the OSGi runtime but are instead encapsulated within the bundle.
As a result, bundling httpasyncclient as an embedded dependency is also removed, since it is no longer required.

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