x11: introduce X11 port

[adamgreloch]

JIRA: RTOS-826

Description

Adds ports of:

• modern X11 libs with fontconfig support
• tinyx xserver
• a set of demo client apps such as:
  • x11-apps (xclock, xeyes, xmessage, xinit, ico, etc.)
  • twm
  • suckless stuff (st terminal, dwm window manager)
  • xbill
  • feh

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: ia32-generic-qemu, ia32-generic-pc

Checklist:

• My change requires a change to the documentation.
• 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).
  build: Add common utility functions, tidy up build process #78
  posix: fix unix socket accept/connect, add their nonblocking variants, handle MSG_PEEK in recv phoenix-rtos-kernel#572
  pc-tty: add framebuffer-based console phoenix-rtos-devices#515
  pc-tty: add PS/2 mouse support and kbd/mouse vdevs phoenix-rtos-devices#512
  ia32: add passing of graphmode params via syspage and platformctl phoenix-rtos-kernel#596
  png: add libpng port #88
• I will merge this PR by myself when appropriate.

[github-actions]

Unit Test Results

7 958 tests  ±0   7 416 ✅ ±0   43m 25s ⏱️ +17s
  470 suites ±0     542 💤 ±0 
    1 files   ±0       0 ❌ ±0 

Results for commit d6e600f. ± Comparison against base commit 1994dc6.

♻️ This comment has been updated with latest results.

[github-actions]

Remaining comments which cannot be posted as a review comment to avoid GitHub Rate Limit

shellcheck

---

📝 [shellcheck] _{reported by reviewdog 🐶}
Double quote to prevent globbing and word splitting. SC2086

phoenix-rtos-ports/tinyx/build.sh

Line 465 in 0e4780d

exec_configure_no_reconf ${configure_opts}

---

📝 [shellcheck] _{reported by reviewdog 🐶}
Use build_freetype "$@" if function's $1 should mean script's $1. SC2119

phoenix-rtos-ports/tinyx/build.sh

Line 537 in 0e4780d

build_freetype

---

📝 [shellcheck] _{reported by reviewdog 🐶}
Use build_expat "$@" if function's $1 should mean script's $1. SC2119

phoenix-rtos-ports/tinyx/build.sh

Line 553 in 0e4780d

build_expat