refactor: move Gradle discovery logic from workspace.js to java_gradle.js

Address review feedback: provider-specific discovery functions don't belong
in workspace.js. Extract traverseForWrapper to tools.js as shared utility,
update base_java.js to delegate to it, and move all Gradle workspace discovery
functions (discoverGradleSubprojects, resolveGradleBinary,
parseGradleInitScriptOutput, GRADLE_INIT_SCRIPT) to their provider file.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: Strum355

src/providers/base_java.js

@@ -144,8 +144,8 @@ export default class Base_Java {
 
 		const useWrapper = getWrapperPreference(this.globalBinary, opts)
 		if (useWrapper) {
-			const manifestPath = path.dirname(this.normalizePath(manifestPath))
-			const wrapper = traverseForWrapper(manifestPath)
+			const manifestDir = path.dirname(this.normalizePath(manifestPath))
+			const wrapper = traverseForWrapper(manifestDir, this.localWrapper)
 			if (wrapper !== undefined) {
 				try {
 					this._invokeCommand(wrapper, ['--version'], {cwd: manifestDir})