Bug 23559 – Add trait to get members from symbol/module with filtering

Adding a trait that allows returning alias symbols (like ``__traits(allMembers)``), but filtered for specific properties would allow for cutting down the costs of reflection code and make it more clear what it is doing. Proposal: ``` __traits(getMembers, symbolOrModuleName, filters) __traits(getMembersRecursive, symbolsOrModuleName, filters) ``` The difference between these two is one goes down nesting, and the other doesn't (shallow vs deep search). Filters are in the form of: ``struct | union | class | fields | function | import`` Ideally, this would be an expression so you can do or's and ands to require things like udas. But not required, only need to offer just one option at a time. Common use cases for this include registration of: web routes, ORM models, CLI handling routines. Preliminary agreement on worthiness by Walter: https://github.com/dlang/dmd/pull/14699#issuecomment-1352683461 This will require isStatic trait to be added to close https://issues.dlang.org/show_bug.cgi?id=16024

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