Sources with `sourceReference > 0` always open in a new buffer

### Debug adapter definition and debug configuration The particular adapter this issue was observed with is a hassle to set up, and this issue should affect any adapter which returns sources that need to be queried for. ### Debug adapter version _No response_ ### Steps to Reproduce 1. Run a configuration which attaches to a debug adapter that returns sources with `sourceReference > 0` 2. Perform an action that causes those sources to be returned and opened (`DapStepInto` with a source being in the current stack frame works) 3. Repeat this action without closing the buffer that was opened ### Expected Result The opened buffer should be reused between `source` actions. ### Actual Result Each time a source's contents is requested through `source`, a new buffer opens. The first is named appropriately, but the following buffers are unnamed.