Support DNS-over-TLS probes in NetworkDiagnostics

Probe DNS servers to see they support DNS-over-TLS. Use system
CAs to verify whether the certificates sent by DNS servers are
trusted or not. An error is thrown to cause the probe failed if
DNS servers send untrusted certificates.

Unlike the DnsResolver which doesn't verify the certificates
in opportunistic mode, all of the DoT probes from NetworkDiagnostics
check certificates.

DoT probes apply to the DNS servers gotten from LinkProperties
and the DoT servers gotten from PrivateDnsConfig whatever private
DNS mode is.

A common example in DNS strict mode:
.  DNS TLS dst{8.8.8.8} hostname{dns.google} src{192.168.43.2:48436} qtype{1} qname{815149-android-ds.metric.gstatic.com}: SUCCEEDED: 1/1 NOERROR (432ms)
F  DNS TLS dst{192.168.43.144} hostname{}: FAILED: java.net.ConnectException: failed to connect to /192.168.43.144 (port 853) from /192.168.43.2 (port 41770) after 2500ms: isConnected failed: ECONNREFUSED (Connection refused) (172ms)
.  DNS TLS dst{8.8.4.4} hostname{dns.google} src{192.168.43.2:37598} qtype{1} qname{759312-android-ds.metric.gstatic.com}: SUCCEEDED: 1/1 NOERROR (427ms)

An example when the CA is not trusted:
F  DNS TLS dst{8.8.8.8} hostname{dns.google}: FAILED: javax.net.ssl.SSLHandshakeException: java.security.cert.CertPathValidatorException: Trust anchor for certification path not found. (16ms)

An example when TCP/TLS handshake timeout:
F  DNS TLS dst{8.8.8.8} hostname{dns.google}: FAILED: java.net.SocketTimeoutException: failed to connect to /8.8.8.8 (port 853) from /192.168.2.108 (port 45680) after 2500ms (2514ms)

Bug: 132925257
Bug: 118369977
Test: atest FrameworksNetTests
Original-Change: https://android-review.googlesource.com/1011670
Merged-In: I1b54abed0e931ca4b8a97149459cde54da1c3d6f
Change-Id: I1b54abed0e931ca4b8a97149459cde54da1c3d6f