[GnoVM/TM2] Limiting package functionality

[leohhhn]

Description

As discussed on the Belgrade retreat, we came to conclusions about pure packages:

• We should forbid direct calls to p/ via maketx call, qeval, or other. In essence, p/ should be only callable by other code (while on this note, we should also forbid the same for stdlibs - reference comment)
• We should panic if p/ tries to get any type of banker (or possibly allow only ReadOnly banker?)
• We should panic if the user tries to change state in a p/, instead of just letting the transaction go through without applying the state change - related issue

cc @moul

[moul]

Can you merge with #2192 ?

[leohhhn]

Closing in favor of #2192