[gbl] add Gbl struct builder

Added `GblBuilder` for `Gbl` construction.
Removed `new()` functions from `Gbl`
Added tests for an AVB verification error.

Bug: 323062115
Test: atest
Change-Id: I7420ff885fe3a65d77ce175a21c1ec214c6292e7
1 file changed
tree: c37d72536d6633b24305e63a00384b5956479fb6
  1. gbl/
  2. libxbc/
  3. vts/
  4. .gitignore
  5. BUILD
  6. OWNERS