Introduce generic image_builder

[nalajcie]

Description

Introduce python-based image builder (plo scripts parsing/generation). Main features:

• single nvm.yaml to describe all Non-Volatile Memory storage in a project
• plo scripts as YAML files with jinja2 templates (only values)
• use internal Elf parser for kernelimg command
• fix some of the incremental build errors, describe some of the project decisions better

Motivation and Context

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Chore (refactoring, style fixes, git/CI config, submodule management, no code logic changes)

How Has This Been Tested?

• Already covered by automatic testing.
• New test added: (add PR link here).
• Tested by hand on: (list targets here).

Checklist:

• My change requires a change to the documentation.
  Building: add new dependencies phoenix-rtos-doc#212
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing linter checks and tests passed.
• My changes generate no new compilation warnings for any of the targets.

Special treatment

• This PR needs additional PRs to work (list the PRs, preferably in merge-order).
• I will merge this PR by myself when appropriate.

[github-actions]

Unit Test Results

7 723 tests  ±0   7 008 ✅ ±0   36m 54s ⏱️ -29s
  443 suites ±0     715 💤 ±0 
    1 files   ±0       0 ❌ ±0 

Results for commit 8474a0e. ± Comparison against base commit bacc9cd.

♻️ This comment has been updated with latest results.