Support language specific intellisense in breakpoints conditions and logMessage peek UI

[weinand]

related issue (but not a duplicate): #11692

Additional info:

• turn current condition text box into an editor (so that we can use the Intellisense infrastructure),
• one way to get Intellisense is to programmatically trigger a completion command for the breakpoint's line and underlying file. From the resulting list of completion items you can extract interesting items (e.g. those with kind Variable) or use all,
• for the LogPoint's text box language Intellisense is only needed within the curly braces:
  { Date.now() }: this is a log message with a variable value: { x }
  Outside of the curly braces Intellisense could just suggest the curly braces.

Example from VS for Mac:

[isidorn]

Done via #46540