Make profile types stricter

[gregtatum]

We should use exact objects and (if possible) covariant (read-only) properties.

e.g. turn this:

export type StackTable = {
  frame: IndexIntoFrameTable[],
  prefix: Array<IndexIntoStackTable | null>,
  length: number,
};

into this:

export type StackTable = {|
  +frame: IndexIntoFrameTable[],
  +prefix: Array<IndexIntoStackTable | null>,
  +length: number,
|};

┆Issue is synchronized with this Jira Task