DEBUG: lua: add tainted flags for stuck Lua contexts

DEBUG: lua: add tainted flags for stuck Lua contexts

William suggested that since we can detect the presence of Lua in the
stack, let's combine it with stuck detection to set a new pair of flags
indicating a stuck Lua context and a stuck Lua shared context.

Now, executing an infinite loop in a Lua sample fetch function with
yield disabled crashes with tainted=0xe40 if loaded from a lua-load
statement, or tainted=0x640 from a lua-load-per-thread statement.

In addition, at the end of the panic dump, we can check if Lua was
seen stuck and emit recommendations about lua-load-per-thread and
the choice of dependencies depending on the presence of threads
and/or shared context.