Codesign: Implement buildbot worker side DMG bundling

Is based on bundle.sh but is adopted to an environment where
codesigning is happening in a dedicated VM.

Also fixed some code from previous commits:

- Removed debug only early output when running commands
- Ensured that path to git is always valid
(wasn't a case when __file__ is relative to current directory).
- Fixed simple code signer which couldn't have imported util.

Codesign: Hook up notarial office

Codesign: Remove DMG codesign signature removal

Codesign tool reports that removing signature is not possible for DMG.

Codesign: Switch to TAR as an interchange format

Allows to preserve file mode through the signing process.

Codesign: Finish codesign step of bundling

Adds all the missing bits from the previous commit, and implements
extra required features: need to copy bundle's _CodeSignatures folder
from codesign machine to the worker machine.

Codesign: Initial implementation of macOS code signer

Main goal of this change is to make codesign step of release signing
to work on macOS. Development is currently was done on Linux based on
looking into what commands are being invoked.

Part of the change which touches other code signing utilities is
related on making it possible to test "foreign" code signers on a
different platform.

MacOS release: Fix typo in codesign instructions

Cleanup: Redundant variable assignment to self

Was triggering strict compiler warning.

Fix T63766: Multiresolution behavior when using crease edge

Switch to Gregory basis patches which are tangent continuous across their
boundaries.

Originally we've used BSpline basis patches to be more compatible with the
old subdivision code, but a lot of things changed anyway.

Blender 2.81a: Update submodule for addons