Address a performance regression in recent upgrade

[lcartey]

getCdsDeclaration() experienced a performance regression in larger codebases with the upgrade to 2.20.4. An example of a partially completed set of tuple counts:

Evaluated relational algebra for predicate CDS::UserDefinedApplicationService.getCdsDeclaration/0#dispred#80b6f393@15836fu7 with tuple counts:
                3237       ~0%    {3} r1 = SCAN containerparent OUTPUT In.1, _, In.0
                3237       ~0%    {3}    | REWRITE WITH Out.1 := 2
                3237       ~1%    {5}    | JOIN WITH `Files::Container.splitAbsolutePath/2#dispred#43b82b7b_021#join_rhs` ON FIRST 2 OUTPUT Lhs.2, Lhs.0, _, Rhs.2, _
                 572       ~0%    {3}    | REWRITE WITH Tmp.2 := "", Tmp.4 := ".cds", Out.2 := InverseAppend(Tmp.2,Tmp.4,In.3) KEEPING 3
                9529     ~232%    {4}    | JOIN WITH containerparent ON FIRST 1 OUTPUT Lhs.2, _, Lhs.1, Rhs.1
                9529     ~234%    {4}    | REWRITE WITH Out.1 := 2
               51748    ~1132%    {3}    | JOIN WITH `Files::Container.splitAbsolutePath/2#dispred#43b82b7b_120#join_rhs` ON FIRST 2 OUTPUT Lhs.2, Lhs.3, Rhs.2
          2969847789    ~1182%    {4}    | JOIN WITH `JSON::JsonValue.getJsonFile/0#dispred#2c4d2f29#bf_10#join_rhs` ON FIRST 1 OUTPUT Rhs.1, Lhs.0, Lhs.1, Lhs.2
            23973500  ~630445%    {3}    | JOIN WITH project#CDL::CdlElement#class#12896241 ON FIRST 1 OUTPUT Lhs.1, Lhs.2, Lhs.3
        568488449775  ~197988%    {3}    | JOIN WITH `Locations::Locatable.getFile/0#dispred#58f05aaa_10#join_rhs` ON FIRST 1 OUTPUT Rhs.1, Lhs.1, Lhs.2
            24415500  ~145193%    {3}    | JOIN WITH CDL::CdlService#ccbb5e6c ON FIRST 1 OUTPUT Lhs.1, Lhs.2, Lhs.0
           891311496  ~306096%    {3}    | JOIN WITH `DataFlowPrivate::Node.getFile/0#dispred#4a057003_10#join_rhs` ON FIRST 1 OUTPUT Rhs.1, Lhs.1, Lhs.2
               95500   ~29220%    {3}    | JOIN WITH CDS::UserDefinedApplicationService#class#e1298e76 ON FIRST 1 OUTPUT Lhs.0, Lhs.1, Lhs.2
                   0       ~0%    {2}    | JOIN WITH `DataFlowPrivate::Node.getFile/0#dispred#4a057003` ON FIRST 2 OUTPUT Lhs.0, Lhs.2
                                  return r1

The join order created a cartesian product on CdlElements and JSON files.

This has been addressed by:

• Using CdlService.getImplementation() to implement UserDefinedService.getCdsDeclaration(). This avoids duplication of logic.
• Update getImplementation() to use a simpler path matching definition, to avoid join order problems.

[jeongsoolee09]

Agree with the changes, thank you!