Zowe Explorer should be programming language agnostic

[phaumer]

Describe the bug

Zowe Explorer provides access to z/OS resources such as MVS data sets and PDS members. You can click on a member to open it in the default VS Code text editor. With its excellent SDK it provides a fantastic platform for extenders to layer their capabilities on top of Zowe Explorer. Zowe Explorer's scope imho is not to provide language specific capabilities such as syntax highlighting or code completion. It therefore needs to be designed language agnostic and not make any assumption about the content of an MVS, USS, or spool file. This would be the responsibility of Zowe Explorer extender extensions to interpret content and decide special behavior such as assuming a program language. Zowe Explorer right now looks at data set names and appends file extensions based on hard coded rules not allowing extenders to control for themselves how a file should be treated.

To Reproduce

1. Create a PDS with COBOL in the name such as IBMUSER.SAMPLE.COBOL
2. Add a JCL file to the data set
3. Open the file: it has a .cbl file extension preventing a JCL language server VS Code extension to appropriately interpret its contents.

Expected behavior

Zowe Explorer should not make any assumptions about the files it opens; other than encodings in UNIX file tags etc.

Screenshots

Desktop (please complete the following information):

• OS: all
• Zowe Explorer Version: v1 to 3
• (Optional) Zowe CLI Version:
• (Optional) Are you using Secure Credential Store?

Additional context

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