Increase default minimum TLS version to 1.2

[axw]

APM Server inherits (most of?) its TLS configuration from libbeat. This includes the minimum/maximum TLS protocol version. These currently default to 1.1 and 1.3 respectively.

TLS 1.1 has been deprecated since 2021, and is considered unsafe. We should bump the minimum to 1.2, but allow users to explicitly opt into setting a minimum version of 1.1 for exotic use cases.

See also https://github.com/elastic/ingest-dev/issues/3474

[kruskall]

Opened #10812 to address the default in APM package.

For APM Server binary and other features using the TLS config struct from elastic-agent-libs, there is an open PR in that repo: elastic/elastic-agent-libs#121