Check compatibility of LineUp 4 string filter object with provenance graph

[thinkh]

With PR lineupjs/lineupjs#274 the return value of a string filter got formalized as IStringFilter. It is now possible to store if the user filtered the string column for missing values. The filter event that tdp_core listens will now return an IStringFilter.

We must check the following points:

• Is the data structure compatible with our tdp_core code (see Parse regular expression filter before storing to provenance graph #301, Regular expression filter not correctly stored in persistent session #306)
• Is it possible to open old sessions (created with LineUp v3) with LineUp 4

[thinkh]

The filter event of LineUp v3 and v4 before PR lineupjs/lineupjs#274 returns a string or a regexp (e.g., AB or /AB/gm).

LineUp v4 with PR lineupjs/lineupjs#274 returns the IStringFilter object (e.g., {filter: "AB", filterMissing: false}, {filter: /AB/gm, filterMissing: false}, or {filter: null, filterMissing: true}). Hence, we must handle these cases and remain backwards compatibility.

[thinkh]

@oltionchampari Please continue my implementation in branch https://github.com/datavisyn/tdp_core/tree/thinkh/331_string-filter-compatibility

• Extend the tests for restoreRegExp in cmds.test.ts so that they support all old AND the new filter interface
• Refactor the restoreRegExp implementation
• Apply the restoreRegExp only to filters in the setColumnImpl function

You can run the tests with npm run test:web:tdp_core from your workspace.