Support collect(role) in InPS evaluation: install and implement TBSS_collect as an iteration symbol

[bero]

OCL collect over a role - self.child->collect(parent), or the implicit form self.child.parent, which BoldOclSemantics rewrites into the same collect node - cannot be evaluated in the persistence layer. CanEvaluateInPS answers False on every engine and Bold falls back to in-memory evaluation, which is correct but fetches the whole intermediate collection for large sets. Split out of #43, where the investigation showed this is a missing feature, not an engine bug.

Current state

• TBSS_collect exists in Source/PMapper/SQL/BoldSqlSymbols.pas only as a commented-out placeholder (one of ~48 TBSS_* names inside a single { } block, lines ~455-520 - not declarations), so nothing installs it in the SQL symbol dictionary. TBoldSqlNodeResolver.VisitTBoldSqlIteration therefore raises InPs SQLSymbol 'collect' not found and TBoldSystemDefaultMapper.CanEvaluateInPS reports False.
• collect(attribute) (self.child->collect(aString)) already works: the OCL semantics turn it into member navigation (TBoldSqlMember), so no iteration node is built.
• The regression test Test.BoldLinks.TTestBoldLinks.TestCanEvaluateInPS_CollectRole_NoFalsePositive pins the current answer (False, all engines) and prints GetBoldLastFailureReason. When this feature lands, that test flips to expecting True and the fetch results must be compared with in-memory evaluation.

Where it slots in

The installed iterations (select, reject, exists, forAll, orderBy) are TBSS_Iteration descendants: ResolveObjectMapper returns Args[0].ObjectMapper (the source collection's class) and BuildWCFOrQuery shapes the loop variable's query (see TBSS_Exists.BuildWCFOrQuery: takes the loop var's query, adds the body's WCF, wraps it as EXISTS). collect(role) differs in one respect: the result is the other end's class, so

• TBSS_collect must become a TBSS_Iteration descendant whose ResolveObjectMapper returns the object mapper of the body expression (Args[1], the role's other end), not of the source;
• BuildWCFOrQuery must produce a query over the other end's table constrained by the link: for a single-valued role stored as an embedded foreign key, a join from the source rows' BOLD_ID to the other end's id column; for a multi-valued role, a join through the link table (or the reverse embedded key on the other end). TBoldLinkDefaultMapper / TBoldDirectMultiLinkDefaultMapper know the columns; TBSS_ListOperations.CreateBoldIdMatchWCF shows the id-matching WCF shape already used for includes;
• the node maker path for the implicit form (BoldOclSemantics.pas sets OperationName := 'Collect') must reach the same symbol - check the name lookup is case-insensitive or aligned;
• duplicates: OCL collect yields a bag; decide whether the SQL form may return distinct ids (Bold object lists are sets of locators anyway) and document it;
• install the symbol in the initialization list next to the other iterations.

Acceptance

• CanEvaluateInPS('self.child->collect(parent)') is True on SQLite and SQL Server; TestCanEvaluateInPS_CollectRole_NoFalsePositive inverted accordingly (and renamed)
• A fetch with the expression as an in-PS condition returns the same object set as in-memory evaluation, for single-valued and multi-valued roles
• Dedicated cases for empty and null links (the fixture has none that the tested expressions traverse)
• The implicit form self.child.parent takes the same path
• TestCanEvaluateInPS_MultiNavigation gets real assertions instead of Assert.Pass
• Full suite green on both engines; scenarios green under DebugUniDAC

Implemented in 27ab038

TBoldSqlSymbol gained LoopVarIsEnclosing and ResolveResultObjectMapper; TBSS_collect is a TBSS_Iteration descendant (loop variable continues the source query, result mapper = body's other end, body query taken over with DISTINCT = set semantics), installed after TBSS_Reject. A body that yields no objects is refused with sCollectBodyMustYieldObjectsInPS. Verified green: SQLite and SQL Server full suites (2181/2179/2 ignored/0 failed), DebugUniDAC fixtures 12/12 and Test.BoldLinks 85/85 over the UniDAC adapter.

[bero]

Implemented in 27ab038 (develop). Body updated: acceptance items ticked, and the "48 declared-but-uninstalled classes" wording corrected - those names sit inside one { } comment block in BoldSqlSymbols.pas (~455-520), they were never declarations. TBSS_collect is now declared next to TBSS_ForAll.

Left open: dedicated test cases for empty and null links traversed by a collect (the current fixture's expressions only cross populated links). Staying open until merged upstream.