tidy-up: Markdown, clang-format nits

- drop leading indent from Markdown.
- switch to Markdown section markers where missing.
- move `&&` and `||` to the end of the line (C, Perl).
- openssl: add parenthesis to an if sub-expression.
- misc clang-format nits.
- unfold Markdown links.
- SSL-PROBLEMS.md: drop stray half code-fence.

Closes #20402

scripts/checksrc.pl

@@ -148,12 +148,12 @@ my %warnings = (
     'BRACEPOS'              => 'wrong position for an open brace',
     'BRACEWHILE'            => 'A single space between open brace and while',
     'COMMANOSPACE'          => 'comma without following space',
-    "CLOSEBRACE"            => 'close brace indent level vs line above is off',
+    'CLOSEBRACE'            => 'close brace indent level vs line above is off',
     'COMMENTNOSPACEEND'     => 'no space before */',
     'COMMENTNOSPACESTART'   => 'no space following /*',
     'COPYRIGHT'             => 'file missing a copyright statement',
     'CPPCOMMENTS'           => '// comment detected',
-    "CPPSPACE"              => 'space before preprocessor hash',
+    'CPPSPACE'              => 'space before preprocessor hash',
     'DOBRACE'               => 'A single space between do and open brace',
     'EMPTYLINEBRACE'        => 'Empty line before the open brace',
     'EQUALSNOSPACE'         => 'equals sign without following space',