Fix ci tests for grass8

[t0b3]

currently ci tests fail for grass8 due to

• missing testdata in test8
• missing grass8 case for mapsets
• wrong crs in info

this PR fixes mapsets(), maps(), vectorLayers() and info()

details see https://cdash.orfeo-toolbox.org/testDetails.php?test=35755260&build=94845

this PR is a prequel for #47887

********* Start testing of TestQgsGrassProvider *********
Config: Using QtTest library 6.2.3, Qt 6.2.3 (x86_64-little_endian-lp64 shared (dynamic) release build; by GCC 12.0.1 20220214 (Red Hat 12.0.1-0)), fedora 36
PASS   : TestQgsGrassProvider::initTestCase()
PASS   : TestQgsGrassProvider::fatalError()
PASS   : TestQgsGrassProvider::locations()
FAIL!  : TestQgsGrassProvider::mapsets() 'verify(ok)' returned FALSE. ()
   Loc: [/root/QGIS/tests/src/providers/grass/testqgsgrassprovider.cpp(454)]
FAIL!  : TestQgsGrassProvider::maps() 'verify(ok)' returned FALSE. ()
   Loc: [/root/QGIS/tests/src/providers/grass/testqgsgrassprovider.cpp(475)]
FAIL!  : TestQgsGrassProvider::vectorLayers() 'verify(ok)' returned FALSE. ()
   Loc: [/root/QGIS/tests/src/providers/grass/testqgsgrassprovider.cpp(502)]
PASS   : TestQgsGrassProvider::region()
FAIL!  : TestQgsGrassProvider::info() 'verify(ok)' returned FALSE. ()
   Loc: [/root/QGIS/tests/src/providers/grass/testqgsgrassprovider.cpp(626)]
PASS   : TestQgsGrassProvider::rasterImport()
PASS   : TestQgsGrassProvider::vectorImport()
PASS   : TestQgsGrassProvider::edit()
PASS   : TestQgsGrassProvider::cleanupTestCase()
Totals: 8 passed, 4 failed, 0 skipped, 0 blacklisted, 9014ms
********* Finished testing of TestQgsGrassProvider *********