[µTVM] Add --runtime=c, remove micro_dev target, enable LLVM backend (#6145)

[µTVM] Add --runtime=c, remove micro_dev target, enable LLVM backend (#6145)

* need to fill address of globals in tvmfuncregistry

* llvm func registry generator works!

* lint fixes

* rm hexdump include

* bring bundle_deploy back to life and add to CI

* revert gcda additions

* git-clang-format

* fix check for --system-lib and test_runtime_micro target

* fixup compile flags for bundle_deploy CRT and improve robustness

* git-clang-format

* add debugging info

* git-clang-format

* initialize ret_values in PackedFunc_Call.

* retrigger CI

* fix log messages

* git-clang-format

* remove default for --runtime target opt

* put backtrace behind a flag and enable it

* simpify ReadString(), fixing bad instruction exception on os x.

* git-clang-format

* uncomment tests

* reorder backtrace ldflags for linux gcc