BackendTLSPolicy conformance test - re-use the tls-backend or deploy as infra

[candita]

See #3212 (comment)

[snorwin]

/assign @snorwin

[snorwin]

@shaneutt, since the PR #3983 is still pending, I’d like to request an extension to include the clean-up in v1.4.0.

[shaneutt]

granted via the parent issue 👍