Add special-case-highlighting parameter to parsing service

[sungshik]

Overview

Before this PR, the semantic highlighter applied a special case for syntax-in-syntax (sub)trees. However, this gave rise to unexpected behavior and caused #456.

After this PR:

• For Rascal, the special case is no longer applied. This fixes Semantic tokenizer makes mistakes when a syntax tree (with category) has syntax children #456.
• For DSLs, the special case continues to be applied for backward-compatibility. That is, for now, no changes are needed to existing grammars. However, users are encouraged to update existing grammars that rely on the special case, as it's deprecated.

To control whether or not the special case is applied for DSLs, this PR temporarily -- for the next few release cycles -- adds keyword parameter usesSpecialCaseHighlighting to constructor parsing of ADT LanguageServer.

• Present release cycle: The default is true. Existing grammars that rely on the special case will have the expected highlighting. They could be updated (encouraged), and usesSpecialCaseHighlighting could be set to true (encouraged).
• Future release cycle (short-term): The default is false. Existing grammars that rely on the special case may not have the expected highlighting. Either they should be updated (encouraged), or usesSpecialCaseHighlighting should be set to true (discouraged).
• Future release cycle (mid-term): usesSpecialCaseHighlighting will be removed (i.e., the special case ceases to exist). Existing grammars that rely on the special case may not have the expected highlighting. They must be updated.

A few details

The updated constructor:

rascal-language-servers/rascal-lsp/src/main/rascal/util/LanguageServer.rsc

Lines 248 to 249 in 9175367

	= parsing(Tree (str _input, loc _origin) parsingService
	, bool usesSpecialCaseHighlighting = true)

The updated docs:

rascal-language-servers/rascal-lsp/src/main/rascal/util/LanguageServer.rsc

Lines 173 to 183 in 9175367

	* Currently, `@category` tags are ignored in the following special case:
	* if a parse tree has a `syntax` non-terminal node `n` with a category
	(either declared as part of `n`, or inherited from an ancestors),
	* and if `n` has a `syntax` non-terminal node `m` as a child,
	* then the category of `n` is ignored in the subtree rooted at `m`
	(regardless of whether a category is declared as part of `m`).
	This special case is deprecated and will be removed in a future release. In
	anticipation of the removal, users that rely on this special case for
	syntax highlighting can update their grammars and explicitly opt-out of the
	special case by passing `usesSpecialCaseHighlighting = false` when
	registering the ((parsing)) service.

The updated Pico language server as an example:

rascal-language-servers/rascal-lsp/src/main/rascal/demo/lang/pico/LanguageServer.rsc

Lines 48 to 50 in 9175367

	set[LanguageService] picoLanguageServer() = {
	parsing(parser(#start[Program]), usesSpecialCaseHighlighting = false),
	documentSymbol(picoDocumentSymbolService),

[sungshik]

Additional comments

[DavyLandman]

LGTM, except that we're missing the typescript side of the dedicated parser configuration.

[sonarcloud]

Quality Gate failed

Failed conditions
13.9% Duplication on New Code (required ≤ 3%)

See analysis details on SonarCloud