tidy-up: miscellaneous

- H3 proxy: re-sync code with original source `curl_ngtcp2.c` to reduce
  differences, and to apply missed minor fixes. Also apply clang-format.
  Drop redundant `#undef`s, casts, `#endif` comments, includes, drop
  intermediate variables, sync include and macro order.
  Follow-up to e78b1b3ecc #21153
- INSTALL-CMAKE.md: move `CURL_ENABLE_SMB` to the enable section.
- tests/http/env: rename `tcpdmp` to `tcpdump` to match object variable.
- mbedtls: drop incorrect `mbedTLS 4+` comments.
  (features are also supported by 3+, meaning it's always supported.)
- lib1648: rename a variable to match purpose.
- CIPHERS.md: alpha-sort link list.
- replace rare `X''` hex markup with `0x`.
- `IP v4/6` -> `IPv4/6`.
- 'version X.Y' -> 'vX.Y', where sensible.
- 'VX.Y' -> 'vX.Y', where sensible.
- fix indents, casing, newlines, typos.

Closes #21772

.github/workflows/linux-old.yml

@@ -116,10 +116,8 @@ jobs:
           echo '::group::raw'; cat bld-1/lib/curl_config.h || true; echo '::endgroup::'
           grep -F '#define' bld-1/lib/curl_config.h | sort || true
 
-      # when this job can get a libssh version 0.9.0 or later, this should get
-      # that enabled again
-      # when this job can get c-ares 1.16.0 or later, we can enable that
-      # again
+      # when this job can get libssh 0.9.0 or greater, this should get that enabled again
+      # when this job can get c-ares 1.16.0 or greater, this should get that enabled again
 
       - name: 'CM configure (out-of-tree, zstd, gssapi)'
         run: |