PLX files are mapped with .pli extension in zowe explorer

Describe the bug

PLX files are mapped with .pli extension in zowe explorer

To Reproduce If DATASET name contains PLX key word, then while accessing member in zowe explorer, the file shows with .pli extension. We have different extension for PL/X and adding .pli extension using wrong extension for editor capabilities.

Expected behavior

For PLX files, associate with .plx file extension

Screenshots

Desktop (please complete the following information):

• OS: MAC
• Zowe Explorer Version: 3.2.2

Mapping is done in following file:

https://github.com/zowe/zowe-explorer-vscode/blob/a4c2c9b6e71fd70c16a207a5ca6fe1a0ac2866b0/packages/zowe-explorer-api/src/fs/types/datasets.ts#L26