Hide certain cell contents from kontrol show and kontrol view-kcfg by default

[JuanCoRo]

Some cell contents can be too huge to allow for a good debugging experience if the contracts under tests are big. In particular, the <jumpDests>, <program>, and <code> cells can be very annoying to ignore.

These cells are rarely deeply inspected, so we could hide their contents by default when printing a node and only show them if a flag like --show-code, --show-program, etc. is passed.

Example: It takes me a solid 25s to scroll through this <jumpDests> cell from kontrol show:

[palinatolmach]

Partially addressed by #720, which replaces <code> and <program> with contract names, if Kontrol is able to look it up.