Fix compiler failing with nested with expression

The previous implementation of `WithParser` used regex, which struggles
with parsing nested structures correctly. This commit improves
`WithParser` to track and parse all nested `with` expressions.

Other improvements:

- Throw meaningful errors when syntax is wrong. Replacing the prior
  behavior of silently ignoring such issues.
- Remove `I` prefix from related interfaces to align with newer code
  conventions.
- Add more unit tests for `with` expression.
- Improve documentation for templating.
- `ExpressionRegexBuilder`:
  - Use words `capture` and `match` correctly.
  - Fix minor issues revealed by new and improved tests:
     - Change regex for matching anything except surrounding
       whitespaces. The new regex ensures that it works even without
       having any preceeding text.
     - Change regex for capturing pipelines. The old regex was only
       matching (non-greedy) first character of the pipeline in tests,
       new regex matches the full pipeline.
- `ExpressionRegexBuilder.spec.ts`:
  - Ensure consistent way to define `describe` and `it` blocks.
  - Replace `expectRegex` tests, regex expectations test internal
    behavior of the class, not the external.
  - Simplified tests by eliminating the need for UUID suffixes/prefixes.

src/application/Parser/Script/Compiler/Expressions/SyntaxParsers/ParameterSubstitutionParser.ts

@@ -6,8 +6,9 @@ export class ParameterSubstitutionParser extends RegexParser {
   protected readonly regex = new ExpressionRegexBuilder()
     .expectExpressionStart()
     .expectCharacters('$')
-    .matchUntilFirstWhitespace() // First match: Parameter name
-    .matchPipeline() // Second match: Pipeline
+    .captureUntilWhitespaceOrPipe() // First capture: Parameter name
+    .expectOptionalWhitespaces()
+    .captureOptionalPipeline() // Second capture: Pipeline
     .expectExpressionEnd()
     .buildRegExp();