pgsql: Run repack_dropped with make and clean up its extension

Run repack_dropped with make and clean up its extension

Commit e5d25959cf8 added the repack_dropped test to Meson but omitted it
from the Makefile, so make-based isolation runs did not execute it. The
test's teardown also left the injection_points extension installed,
relying on a later test to remove it.

Add repack_dropped to the Makefile's isolation tests and drop the
extension during teardown.

Author: Fujii Masao <masao(dot)fujii(at)gmail(dot)com>
Reviewed-by: Álvaro Herrera <alvherre(at)kurilemu(dot)de>
Discussion: https://postgr.es/m/CAHGQGwG9bHxhs4Nj+9avSjSGh0vdYNQgEuz+pmJ-H5be6tEBTw@mail.gmail.com
Backpatch-through: 19

Branch
------
REL_19_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/3cf7d89d6b6ef3077e62aa11c7be71f918b6e303

Modified Files
--------------
src/test/modules/injection_points/Makefile | 1 +
src/test/modules/injection_points/specs/repack_dropped.spec | 1 +
2 files changed, 2 insertions(+)