[fingerprint] - App detection

[weikanglim]

Part of #705

Application detection package

Application detection that scans the filesystem for application projects linkable to azure.yaml. Application detection also collects useful additional metadata about services for infra generation.

Description:

1. Detection involves scanning the filesystem for well-known file names/types (requirements.txt, pom.xml, *.*proj).
2. In some cases, we would read build-tooling project metadata to get more precise detection.
   1. In general, we should prefer accuracy over performance. If reading *.csproj provides a better accurate detection than inferring from other means, we should do it.
3. When walking directories, we apply heuristics such as: avoiding hidden directories, well-known directories like (eng, tools) to avoid picking up tooling that aren't production applications.
4. Application detection generates additional metadata about services for infra generation.

The per-directory detection logic is currently intentionally simple and isn't as complete as something that Oryx provides. In the future,, the per-directory detection logic will leverage the common library Oryx provides.

[weikanglim]

WIP is here: #2457. Remainder work is to clean up for production, reviewed and delivered.