getdns: migrate to Conan v2, bump to v1.7.3

[valgur]

• Requires libidn2: migrate to Conan v2, add shared MSVC build #18642

[uilianries]

I did some changes over this PR, including:

• Replaced cmake wrapper by CMAKE_PROJECT_INCLUDE to include external dependencies
• Simplified test package to avoid fetching the network
• Remove option for tls: GnuTLS is only supported on Linux and needs libnuma to work. Checking other package managers, only Gentoo is supporting it, and still, has a separated package for gnutls-numa
• Remove stub option and configured to True always. Other package managers are using True as well, and CCI has no libunbound available
• Enable libidn2 by default, following the upstream
• Injected compiler flag to ignore pointer error on Clang (reported to the upstream)
• Imported libidn2 definition when building on Windows to avoid linkage error.

[uilianries]

LGTM

[valgur]

LGTM as well. Thanks!

[conan-center-bot]

Conan v1 pipeline ✔️

All green in build 7 (6092f1d143ca2e1f14dcbd1e6cb012cd9434e0d7):

• getdns/1.7.3:
  All packages built successfully! (All logs)

---

Conan v2 pipeline ✔️

Note: Conan v2 builds are now mandatory. Please read our discussion about it.

All green in build 6 (6092f1d143ca2e1f14dcbd1e6cb012cd9434e0d7):

• getdns/1.7.3:
  All packages built successfully! (All logs)