Better Burn-related .nupkg names

[robmen]

User story

• As a setup developer, using the standard bootstrapper applications is a matter of referencing the WixToolset.BootstrapperApplications.wixext package instead of the more cryptic WixToolset.Bal.wixext.
• As a setup developer, creating a custom bootstrapper uses less cryptic package references like WixToolset.BootstrapperApplicationApi.

Proposal

A major theme of WiX v5 is to fix many of the bootstrapper application issues introduced in WiX v4. Moving bootstrapper applications out of proc with #7916 is a huge step. It is also a significant breaking change. Given the goal of few to no breaking changes in WiX releases, WiX v5 is the best opportunity to fix any Burn-related issues.

One of the Burn-related DX issues is that the existing .nupkg names are very cryptic with names like WixToolset.BalUtil, WixToolset.Mba.Core, and WixToolset.Bal.wixext for use by native and managed bootstrapper applications plus access to the standard bootstrapper applications. The following is the list of .nupkgs being renamed and, in some cases, split:

• WixToolset.BextUtil renamed WixToolset.BootstrapperExtensionApi. Additionally, all references to "bundle extension" renamed to "bootstrapper extension" to align with "bootstrapper applications".
• WixToolset.BalUtil and WixToolset.Mba.Core merged and renamed WixToolset.BootstrapperApplicationApi. Additionally, BA functions are extracted from balutil.lib into a new WixToolset.WixStandardBootstrapperApplicationFunctionApi package.
• WixToolset.Bal.wixext renamed WixToolset.BootstrapperApplications.wixext

Considerations

• For backward compatibility, WixToolset.BootstrapperApplications.wixext will still use the http://wixtoolset.org/schemas/v4/bal namespace.
• For backwards compatibility, WixToolset.Bal.wixext will continue to be published, but it carries a copy of the WixToolset.BootstrapperApplications.wixext.dll to be passed to the compiler. This could allow a user to incorrectly PackageReference both WixToolset.BootstrapperApplications.wixext and WixToolset.Bal.wixext and get a conflict.