Update deprecated EXT_ITER option in test configs

[Syphonicc]

EXT_ITER was removed in SU2 v7 and replaced by ITER. These eight configs still used the old name and failed to parse. Values are unchanged; this is a rename only.

All eight verified to run on current develop with a serial build.

Proposed Changes

EXT_ITER was removed in SU2 v7 and replaced by ITER, but eight test configs still used the old name and fail to parse with a "invalid option name" error. This renames the option in each; iteration values are unchanged, so there's no behavioral change.

Files updated:

control_surface/inv_ONERAM6_moving.cfg
control_surface/inv_ONERAM6_setting.cfg
euler/CRM/inv_CRM_JST.cfg
euler/channel/inv_channel.cfg
navierstokes/naca0012/lam_NACA0012.cfg
rans/flatplate/turb_SST_flatplate.cfg
rans/s809/turb_S809.cfg
rans_uq/naca0012/turb_NACA0012_uq.cfg

All eight were run locally on current develop (serial build) and start and converge normally.

Two things I noticed while doing this, not addressed here , happy to open separate issues if useful:

Several other configs have further deprecated options (FROZEN_VISC, REF_LENGTH_MOMENT, GEO_AXIS_STATIONS, SOLUTION_LIN_FILENAME) and some have solver/turbulence-model settings that no longer validate.
The hom_euler test cases reference mesh files that don't appear to exist in either the SU2 or TestCases repos, so those can't be run or verified.

Related Work

None.

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