Add GBL interfaces for block device, console, boot

Adds interfaces in GblOps for acessing platform block devices, reading
and writing platform console and platform specific boot. Also sets up
basic integration tests for libgbl.

Bug: b/334962166

Change-Id: I2aa1974599af47a619ca3b7e905f6b8055f5951a
23 files changed
tree: 44a8186dabf7b8f1329e4318f532b2acf8cb99af
  1. gbl/
  2. libxbc/
  3. vts/
  4. .gitignore
  5. BUILD
  6. OWNERS