Introduce multi-endpoint servers and health check endpoints to HttpServerSourceStage

[jadu-nv]

Description

Addresses: #1732

Currently, the HttpServer implementation does not support the initialization of a single server with multiple endpoints. This PR seeks to address this issue by refactoring the HttpServer by taking a list of HttpEndpoint objects (encapsulates the attributes of an http endpoint, ie. url, method, endpoint handler).

Additionally, this PR also introduces 2 endpoints to HttpServerSourceStage that allows users to conduct health checks on their pipelines.

• GET /live -> Immediately returns a 200 response if the server is alive
• GET /ready -> Immediately returns a 200 response if the server is ready to accept new messages

These endpoints are configurable by the user.

By Submitting this PR I confirm:

• I am familiar with the Contributing Guidelines.
• When the PR is ready for review, new or existing tests cover these changes.
• When the PR is ready for review, the documentation is up to date with these changes.

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[mdemoret-nv]

/ok to test

[jadu-nv]

/ok to test

[dagardner-nv]

/ok to test

[dagardner-nv]

/ok to test

[dagardner-nv]

/merge