Additional cleanup for error-prone descriptions

[Philzen]

Following the discussion in openrewrite/rewrite-docs#282

The error-prone template descriptions by picnic seem to need some more treatment. See this example for https://docs.openrewrite.org/recipes/tech/picnic/errorprone/refasterrules/testngtoassertjrulesrecipes:

TODOs:

• remove leading and trailing underscore
• remove any <p> tags
• convert the <pre>-block to a markdown code block and remove the surrounding {@code … } custom tag

openrewrite/rewrite-docs@5925d43 sort of already describes a good test case.

[timtebeek]

Thanks for logging the issue separately; providing the context & links from the other issue for quick reference:

• The JavaDoc for the original Refaster rule
• This JavaDoc is then extracted into a recipe description with some light modifications already
  

  rewrite-templating/src/main/java/org/openrewrite/java/template/processor/RefasterTemplateProcessor.java

  Lines 439 to 461 in 7eceffc

  	// Extract from JavaDoc
  	Tokens.Comment comment = cu.docComments.getComment(classDecl);
  	if (comment != null && comment.getText() != null && !comment.getText().isEmpty()) {
  	String commentText = comment.getText()
  	.replaceAll("\\{@\\S+\\s+(.*?)}", "`$1`")
  	.replace("\\", "\\\\")
  	.replace("\"", "\\\"")
  	.replace("\b", "\\b")
  	.replace("\t", "\\t")
  	.replace("\f", "\\f")
  	.replace("\r", "\\r");
  	String[] lines = commentText.split("\\.\\R+", 2);
  	displayName = lines[0].trim().replace("\n", "");
  	if (displayName.endsWith(".")) {
  	displayName = displayName.substring(0, displayName.length() - 1);
  	}
  	if (lines.length > 1 && !lines[1].trim().isEmpty()) {
  	description = new StringBuilder(lines[1].trim().replace("\n", "\\n"));
  	if (!description.toString().endsWith(".")) {
  	description.append('.');
  	}
  	}
  	}

• The description is converted into Markdown in this generator, which should already account for the _ 🤔

All in all this will require some fixes both here and in the markdown generator, before they show up as fixed in the docs.