ngtcp2: adjust config and code checks for ngtcp2 without nghttp3

- make configure show on HTTP3 feature that both ngtcp2 and nghttp3
are in play
- define ENABLE_QUIC only when USE_

ngtcp2: adjust config and code checks for ngtcp2 without nghttp3

- make configure show on HTTP3 feature that both ngtcp2 and nghttp3
are in play
- define ENABLE_QUIC only when USE_NGTCP2 and USE_NGHTTP3 are defined
- add USE_NGHTTP3 in the ngtcp2 implementation

Fixes #10793
Closes #10821

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quic: rename vquic implementations, fix for quiche build.

- quiche in debug mode did not build, fixed.
- moved all vquic implementation files to prefix curl_* to avoid
the potentia

quic: rename vquic implementations, fix for quiche build.

- quiche in debug mode did not build, fixed.
- moved all vquic implementation files to prefix curl_* to avoid
the potential mixups between provided .h files and our own.
- quich passes test 2500 and 2502. 2501, the POST, fail with
the body being rejected. Quich bug?

Closes #10242

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