Add Xcode project for Teleport Verify; add gomobile as tool dep (#67750)

* Generate Xcode project for Verify

* Set Swift version to 6; remove macOS and Vision as destinations

* Handle `teleport://` links and add enrollment screen

* Avoid building macOS-specific stuff on iOS

This is needed for gomobile to build our stuff from lib/mobile from the
next commit.

* Add `lib/mobile/verify/enroll` compiled with gomobile

* `lib/mobile`: Temporarily use private Device Trust service

The public gRPC service exists on the demo branch but not on this
branch. In order to make it possible to compile
`lib/mobile/verify/enroll`, temporarily use the private service which
has similar RPCs.

* Run `make go-mod-tidy-all`

* Make Swift app connect to public DT service on "Request Now" tap

* mobile: Add sheet for enroll request status

* Revert go.mod changes

This reverts commit b9af7a7614 and
2c00ecd7fa.

* Add `build.assets/tools/gomobile`

* Move gomobile back to main go.mod

This reverts commits 9b2a6c4ea3 and
a83c2959fa.

Makefile

@@ -2131,3 +2131,7 @@ ifndef BENCH_FILES
 	$(error "Please provide BENCH_FILES=<file1> <file2> ...")
 endif
 	@$(BENCHSTAT) $(BENCH_FILES) | tee test-logs/benchstat.txt
+
+.PHONY: mobile/Verify/Verify/gen/Enroll.xcframework
+mobile/Verify/Verify/gen/Enroll.xcframework:
+	go tool gomobile bind -target=ios -o $@ github.com/gravitational/teleport/lib/mobile/verify/enroll