girepository: Rename g-ir-generate and g-ir-inspect

Rename them to `gi-decompile-repository` and `gi-inspect-repository` to
match the existing `gi-compile-repository`. The names have to differ
from those used in girepository-1.0 to avoid collisions.

‘generate’ has been changed to ‘decompile’ because it does the inverse
of what `gi-compile-repository` does: it converts a typelib to a GIR
file. ‘generate’ never really made much sense for this anyway — it’s
almost a synonym of ‘compile’.

Signed-off-by: Philip Withnall <pwithnall@gnome.org>

Helps: #3155

girepository/meson.build

@@ -243,3 +243,5 @@ if build_tests
 endif
 
 subdir('compiler')
+subdir('decompiler')
+subdir('inspector')