cmake: fix clang-tidy builds to verify tests, fix fallouts

- cmake: disable test bundles for clang-tidy builds.
  clang-tidy ignores #included .c sources, and incompatible with unity
  and bundles. It caused clang-tidy ignoring all test sources. It also
  means this is the first time tests sources are checked with
  clang-tidy. (autotools doesn't run it on tests.)

- cmake: update description for `CURL_TEST_BUNDLES` option.

- fix tests using special `CURLE_*` enums that were missing from
  `curl/curl.h`. Add them as reserved codes.

- fix about ~50 other issues detected by clang-tidy: unchecked results,
  NULL derefs, memory leaks, casts to enums, unused assigments,
  uninitialized `errno` uses, unchecked `open`, indent, and more.

- drop unnecessary casts (lib1533, lib3207).

- suppress a few impossible cases with detailed `NOLINT`s.

- lib/escape.c: drop `NOLINT` no longer necessary.
  Follow-up to 72abf7c13a #13862 (possibly)

- extend two existing `NOLINT` comments with details.

Follow-up to fabfa8e402 #15825

Closes #16756

docs/INSTALL-CMAKE.md

@@ -240,7 +240,7 @@ target_link_libraries(my_target PRIVATE CURL::libcurl)
 - `CURL_LTO`:                               Enable compiler Link Time Optimizations. Default: `OFF`
 - `CURL_STATIC_CRT`:                        Build libcurl with static CRT with MSVC (`/MT`) (requires UCRT, static libcurl or no curl executable). Default: `OFF`
 - `CURL_TARGET_WINDOWS_VERSION`:            Minimum target Windows version as hex string.
-- `CURL_TEST_BUNDLES`:                      Bundle `libtest` and `unittest` tests into single binaries. Default: `OFF`
+- `CURL_TEST_BUNDLES`:                      Build tests into single-binary bundles. Default: `OFF`
 - `CURL_WERROR`:                            Turn compiler warnings into errors. Default: `OFF`
 - `ENABLE_CURLDEBUG`:                       Enable TrackMemory debug feature. Default: =`ENABLE_DEBUG`
 - `ENABLE_CURL_MANUAL`:                     Build the man page for curl and enable its `-M`/`--manual` option. Default: `ON`