When preparing to insert, allocate non-inlined default values in executo...

...r-scoped pool.

My performance fix for the insert/materialize node refactoring was allocating non-inlined temp strings in the temp pool.  The lifetime of this memory was not long enough, and valgrind was showing invalid pointer reads as a result.

Yes, you are right.  Thanks for catching this.  My optimization to cache the template tuple broke DEFAULT NOW.