Track build info and SSL capabilities of `libupsclient` actually used by the clients, add SSL tests with NIT where possible

[jimklimov]

• Library version tracking/reporting: loosely related to Experiment building NUT with shared private libraries #3251 where we track the version in private libs separately (in case that code is not built into the binaries but is rather shared)
• Library SSL capability: we may request it with upscli_init() and then upscli_sslinit() or upscli_ssl() for a particular connection, and may fail (e.g. if that is not built in or not configured on the client side) but might never know why exactly it failed (e.g. lack of ability in the library; note that UPSCLI_ERR_SSLFAIL and zero returns from upscli_sslinit() are about lack of server ability... or lack of library ability in the latter case)
• NIT suite test-cases: to serve as practical set-up documentation as well as cross-platform check about upsd and upsc (etc.) SSL setups. => see also CI: actively test SSL setups with NIT #1711