Problem: Vim9: not enough testing for profiling.
Solution: Add a test with nested functions and a lambda. Fix profiling
for calling a compiled function.
Problem: Vim9: compiled functions are not profiled.
Solution: Add initial changes to profile compiled functions. Fix that a
script-local function was hard to debug.
Problem: Reallocating the list of scripts is inefficient.
Solution: Instead of using a growarray of scriptitem_T, store pointers and
allocate each scriptitem_T separately. Also avoids that the
growarray pointers change when sourcing a new script.
Problem: Execution stack is incomplete and inefficient.
Solution: Introduce a proper execution stack and use it instead of
sourcing_name/sourcing_lnum. Create a string only when used.
Problem: Not easy to jump to function line from profile.
Solution: Use "file:99" instead of "file line 99" so that "gf" works.
(Daniel Hahler, closes#4951)
