Adds lang service switch

[lewis-sanchez]

This PR fixes #17298

This PR adds a new setting to the MSSQL extension that allows users to have the language mode set to none by default

New query editors that are opened when this setting is enabled, will have "None" as the chosen language

Previously saved query files that are opened when this setting is enabled, will also have "None" as the chosen language

To enable the MSSQL language mode for an editor, first click on "None" in the status bar, and then choose MSSQL as the language

[github-actions]

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[aasimkhan30]

Maybe we need some PM feedback on this.

Currently this option sets intellisense language to 'none' for all sql editors.

However, there are 2 conditions which should always have 'mssql' intellisense enabled.

1. if we open a query editor from a OE context menu, it should launch as MSSQL editor always.
   
2. if user specifically opens an MSSQL editor from command line, it should still have the language set to MSSQL.
   

Maybe this option should only apply to .sql files opened from disk as those files can belong to any database provider (PGSQL, MYSQL....)

[lewis-sanchez]

@aasimkhan30, here's another GitHub issue that is related to the concern you're pointing out. (#801).

This PR was intended to add a switch to optionally set the language mode to "None" as the default, instead of MSSQL when opening editors. The new switch that is added by this PR is initially turned off, meaning that MSSQL will be the default language mode when editors are opened.

[kburtram]

@aasimkhan30, here's another GitHub issue that is related to the concern you're pointing out. (#801).

This PR was intended to add a switch to optionally set the language mode to "None" as the default, instead of MSSQL when opening editors. The new switch that is added by this PR is initially turned off, meaning that MSSQL will be the default language mode when editors are opened.

How does #801 address the point Aasim mentions regarding opening editors with an MSSQL connection? I think in those scenarios the language mode should probably be MSSQL regardless of this setting. I think this setting is more relevant for non-connected SQL files.

[kburtram]

I think we need to do a design review on Intellisense settings and how to handle connections for new SQL documents. And how best to handle non-MSSQL compatible SQL files. This seems like part of the solution but maybe should be a little different than currently implemented.

[Benjin]

Closing PR as we revisit the design