Unified Storage: in SQL template, also handle output data, improve API, examples and docs (#87560)

* preview of work so far

* stylistic improvements

* fix linters

* remove golden tests, they may cause the system to be too rigid to changes

* remove unnecessary code for golden tests

* remove white space mangling in Execute

* also handle output data, improve API, examples and docs

* add helper methods

* fix interface

pkg/services/store/entity/sqlstash/sqltemplate/dialect_test.go

@@ -91,7 +91,7 @@ func TestRowLockingClauseAll_SelectFor(t *testing.T) {
 
 		{
 			input:  splitSpace(string(SelectForShare)),
-			output: SelectForShare,
+			output: "FOR " + SelectForShare,
 		},
 	}