cmake: extend zlib's `AUTO` option to brotli, zstd and enable if found

cmake: extend zlib's `AUTO` option to brotli, zstd and enable if found

- make `curl_dependency_option()` more generic.

- extend `CURL_BROTLI` and `CURL_ZSTD` options to accept
  `AUTO` in addition to existing `ON` and `OFF`.

- change `CURL_BROTLI` and `CURL_ZSTD` option default
  to `AUTO`. Was: `OFF`.
  It brings cmake behavior closer to `./configure`.
  Still different:
  - `./configure` defaults to `off` which means to check default
    locations. cmake checks more locations by default.
    (Also tried `NO_CMAKE_PATH`, but then it checked less locations.)
  - cmake returns both `brotlicommon` and `brotlidec` libs,
    while `./configure` only returns the latter.

- ci: drop explicit cmake options, that are now unnecessary.

- GHA/configure-vs-cmake: make adjustments to make tests pass.

Closes #15431