test: allow disabling IP versions in iohandle test (#19657)
test: allow disabling IP versions in iohandle test (#19657)

The test case "IoSocketHandleImplTest" attempts to open a TCP socket
listening on the loopback interface, parameterized over both IPv4 and
IPv6.  This does not respect configuration in the environment variable
"ENVOY_IP_TEST_VERSIONS".  As a result, test cases run with
"ENVOY_IP_TEST_VERSIONS=v4only" still attempt to open an TCP with an
IPv6 address, failing in IPv4-only environmnents.

It seems like the canonical way to parameterize the IP versions is to
simply use the output of "TestEnvironment::getIpVersionsForTest()" as
the test parameter set.  After applying this patch, the IPv4-only
environment I am using for development passes tests on v1.21.0.

Signed-off-by: Noah Goldman <afb8c82a9efdcb1f7cf6e13f6bd9cef171e752e5@uber.com>
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