[test host utils] use make_shared to avoid memory leaks (#14042)
[test host utils] use make_shared to avoid memory leaks (#14042)

Commit Message: Switch to using std::make_shared in host util test code. Clang tidy is unhappy about current state of code and has been complaining about potential memory leaks, sample log here: https://dev.azure.com/cncf/envoy/_build/results?buildId=57303&view=logs&jobId=b7634614-24f3-5416-e791-4f3affaaed6c&j=b7634614-24f3-5416-e791-4f3affaaed6c&t=21e6aa7d-f369-5abd-5e4e-e888cac18e9c. Issue discovered in this PR. We may need to create dedicated issue to fix problem globally.
Risk Level: Low
Testing: Covered by existing tests
Docs Changes: NA
Release Notes: NA

Signed-off-by: Kateryna Nezdolii <b60d69667d80133a6a94d5136ecb626d5c840307@spotify.com>

lyft/envoy,envoyproxy/envoy,envoyproxy/envoy,envoyproxy/envoy,envoyproxy/envoy,envoyproxy/envoy,lyft/envoy,envoyproxy/envoy,envoyproxy/envoy,envoyproxy/envoy,lyft/envoy,envoyproxy/envoy,lyft/envoy,envoyproxy/envoy,envoyproxy/envoy,lyft/envoy,envoyproxy/envoy,lyft/envoy