Convert a temporal point between geography and geometry on the generated surface

[estebanzimanyi]

GeneratedSurfaceTest calls tgeogpoint_to_tgeompoint and tgeompoint_to_tgeogpoint, which answer
what tgeompoint(tgeogpoint) and tgeogpoint(tgeompoint) answer in MobilityDB. A linear lon/lat
trip from POINT(80 -30) to POINT(179 -30) crosses the envelope POLYGON((93.41 -60.55, 173.34
-60.55, 173.34 -8.47, 93.41 -8.47, 93.41 -60.55)) only between its two instants: converted to a
temporal geometry point it stays linear and ever intersects the envelope, the step trip with the
same instants does not, and converting back gives the trip it started from.

Witness: a table of flights holds tgeogpoint values, and comparing them with a lon/lat envelope
or reprojecting them to a planar SRID needs them as tgeompoint; the generated surface named no
conversion between the two point types, and tgeography_to_tgeogpoint refuses a tgeogpoint
("The temporal value must be of type tgeography"). MobilityDB #2994 states the two conversions
in MEOS.

Measured: tools/refresh-from-master.sh over MobilityDB master a0860d4731, MEOS-API 0438baabc6 and
JMEOS bade99212b, then mvn -B clean test: 35 tests, 0 failures, 0 errors, 0 skipped, the new case
among the 18 of GeneratedSurfaceTest.

Why: the conversion keeps the interpolation of the trip, so a query on the converted trip answers
for the motion between the instants, and the step control is what shows it does.