Refactor V2ServerAPICalls/NuGetServerAPICalls to use object-oriented query builder (instead of string manipulation)

[sean-r-williams]

Summary of the new feature / enhancement

Currently, V2ServerAPICalls and NuGetServerAPICalls build NuGet v2 API call URLs through direct manipulation of the query URL. This has several limitations:

• Potential URL encoding errors
• Fencepost-class problems where combining operators (and, etc.) are emitted at inappropriate places (see Unable to install packages with dependencies from Artifactory PSGallery mirror (NuGet v2) #1633 for an example of this)

Moving to an object-oriented approach would make these problems easier to avoid altogether.

Proposed technical implementation details (optional)

Refactor V2ServerAPICalls/NuGetServerAPICalls to:

• Utilize some type of container (List<String>, HashSet<String>, or similar) to hold query clauses, then build a formatted query with combining operators in the appropriate places
• Handle URL encoding through either:
  • Off-label use of HttpValueCollection to dynamically build a query string (with built-in URL-safe encoding)
  • Direct serialization of key-value pairs with Uri.EscapeDataString