.lib libraries added as "KiCad" instead of "Legacy" to the library table

Note: The issue is that when adding a ".lib" library to the library table, the column "Library Format" is defaulted to "KiCad" rather than "Legacy". This means when you press "Migrate Libraries", it thinks that the selected library has already been converted.

Original Report:

Title was: "Migrate" button on Symbols Library Manage does not work as expected

Description

I am converting projects from v5.1 to v5.99. Despite checking the rescue option to use old symbols, my personal library symbols where not there. I went to add the library manager to add my "fnd_library) by pointing to it in the correct folder and adding it to the bottom of the list (it is fnd_library.lib). When I press the "migrate" button, is just goes into a loop popping up this dialog box saying I have to find a library ending in .lib. I finally gave up and found a way to do it differently by clicking on the symbol, going into the edit menu, and choosing "update symbol". I then pointed to correct library. I may have imported the library first, I don't remember how the library finally got converted from xxx.lib to xxx.kicad.sim, but I may have unchecked every one of the libraries leaving only the old one and only then the migrate worked. If this is the case, we need an "uncheck all" and "check all" button.

Steps to reproduce

Find a .lib file, add it to the list of libraries. Highlight that one and click the migrate button. It will just say you need to select a .lib file.

KiCad Version

Application: KiCad (64-bit)

Version: (5.99.0-11145-g173c9a974c), release build

Libraries:
	wxWidgets 3.1.5
	libcurl/7.74.0-DEV Schannel zlib/1.2.11

Platform: Windows 10 (build 18362), 64-bit edition, 64 bit, Little endian, wxMSW

Build Info:
	Date: Jun 26 2021 09:00:22
	wxWidgets: 3.1.5 (wchar_t,STL containers)
	Boost: 1.75.0
	OCC: 7.5.0
	Curl: 7.74.0-DEV
	ngspice: 34
	Compiler: Visual C++ 1928 without C++ ABI

Build settings:
	KICAD_USE_OCC=ON
	KICAD_SPICE=ON