Reject unbalanced parentheses in profile expressions

[daguimu]

Problem

ProfilesParser silently accepts unbalanced parentheses in profile expressions. For example, Profiles.of("dev)") or @Profile("dev)") is accepted without error and treated as "dev". This can lead to unexpected behavior where malformed profile annotations are silently interpreted instead of being rejected.

Root Cause

In ProfilesParser.parseTokens(), when a closing ) is encountered outside of a Context.PARENTHESIS context (i.e., without a matching opening (), the parser merges the current elements, clears state, and continues parsing instead of raising a validation error. Similarly, when all tokens are consumed while still inside a PARENTHESIS context (unmatched opening (), the method returns normally without detecting the imbalance.

Fix

• In the ")" case of parseTokens(), reject unmatched closing parentheses by calling assertWellFormed(expression, false) when not in PARENTHESIS context, instead of silently continuing
• After the token loop, add assertWellFormed(expression, context != Context.PARENTHESIS) to reject unmatched opening parentheses when tokens are exhausted
• Fix an existing test (ofAndExpressionWithoutSpaces) that inadvertently relied on this lenient behavior by using "spring&framework)" instead of "(spring&framework)"

Tests Added

Change Point	Test
Reject unmatched ) at top level	malformedExpressionsWithUnbalancedParentheses() — verifies "dev)", "spring&framework)", "(dev))" all throw IllegalArgumentException
Reject unmatched ( when tokens exhaust	malformedExpressionsWithUnbalancedParentheses() — verifies "(dev", "((dev)" throw IllegalArgumentException
Fix existing test input	ofAndExpressionWithoutSpaces() — now uses "(spring&framework)" and still passes assertAndExpression checks

All 37 tests in ProfilesTests pass, including all pre-existing tests (no regressions).

Impact

Expressions with unbalanced parentheses that were previously silently accepted will now throw IllegalArgumentException with a "Malformed profile expression" message. This is consistent with the existing behavior for standalone "(" and ")" which already throw. Well-formed expressions are not affected.

Fixes #36540