wolfssl: support CA caching

As a bonus, add SSLSUPP_CA_CACHE to let TLS backends signal its support
for this so that *setopt() return error if there is no support.

Closes #13786

lib: merge `ENABLE_QUIC` C macro into `USE_HTTP3`

Before this patch `lib/curl_setup.h` defined these two macros right
next to each other, then the source code used them interchangeably.

lib: merge `ENABLE_QUIC` C macro into `USE_HTTP3`

Before this patch `lib/curl_setup.h` defined these two macros right
next to each other, then the source code used them interchangeably.

After this patch, `USE_HTTP3` guards all HTTP/3 / QUIC features.
(Like `USE_HTTP2` does for HTTP/2.) `ENABLE_QUIC` is no longer used.

This patch doesn't change the way HTTP/3 is enabled via autotools
or CMake. Builders who enabled HTTP/3 manually by defining both of
these macros via `CPPFLAGS` can now delete `-DENABLE_QUIC`.

Closes #13352

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tls: use shared init code for TCP+QUIC

Closes #13172

vquic: extract TLS setup into own source

- separate ngtcp2 specific parts out
- provide callback during init to allow ngtcp2 to apply its defaults

Closes #12678