State what a wrapper binds for each number of arguments its tests of PG_NARGS() decide

[estebanzimanyi]

A wrapper can choose what it reads by any test of PG_NARGS(), and by the else of such a test:
Temporal_app_tinst_transfn starts maxdist from -1.0 and maxt from NULL and, under
if (PG_NARGS() > 3), reads maxt from argument 3 under if (PG_NARGS() == 4) and, in its else,
maxdist from argument 3 and maxt from argument 4. _guards of parser/boundargs.py states for each
statement the numbers of arguments it runs for: every conjunct testing PG_NARGS() with ==, !=,
<, <=, > or >= narrows them, the else of a test of PG_NARGS() alone runs for the others, nested
tests intersect, and comments are read as blanks. A local starting from a literal is that
literal for a signature of a number of arguments none of its later assignments runs for
(_guarded_default), and _caller_index reads, for a signature, only the assignments a call of its
number of arguments runs. appendInstantTransition(tbool, tbool, text, interval) therefore binds
maxdist to -1.0, and its argument 3 left to a NULL default passes NULL for maxt, where the
catalog stated no bind and paired argument 3 with maxdist.

The floor of .github/workflows/pytest.yml rises to 536, the suite collecting the two tests of
ArityBranchTests, which read the wrapper of Temporal_app_tinst_transfn.

Witness: over MEOS-API ffa1f6f the seven signatures appendInstantTransition(T, T, text,
interval) state no boundArgs, so a binding pairs their three SQL arguments after the state with
the four parameters interp, maxdist and maxt and finds no overload; tpcpoint's states
nullDefaultBinds {"3": {"maxdist": "-1.0"}} for its interval argument.

Measured over MobilityDB master 3a8e6dba09, run.py on upstream ffa1f6f and on this branch with
the same headers: the two catalogs differ in temporal_app_tinst_transfn alone, the seven
signatures of four arguments binding maxdist to -1.0, tpcpoint's argument 3 passing NULL for
maxt, and the nine of five arguments stating that argument 4 passes NULL for maxt. The suite
collects 536 tests, 451 passing and 85 skipped without a catalog in output/.

Why: a binding calls appendInstantAgg with an interpolation and a gap interval as PostgreSQL
does only when the catalog states the distance the wrapper passes for that call.