Completion: empty record fixes

[auduchinok]

Continuation of #12865.

Fixes field items in empty records:

type Record =
    { Field: int }

{ {caret} } // complete `Field`

Fixes env lookup at the first field location:

type Record =
    { Field: int }

let record = { Field = 1 }

{ {caret} } // complete `record`

type Record =
    { Field: int }

let record = { Field = 1 }

{ re{caret} } // complete `record`

[auduchinok]

This is ready too now.