tools: escape Python string backslashes

[Old-Ding]

Summary

• use raw regex strings in the licensing helpers to avoid Python invalid escape warnings
• escape the backslashes in the IAR project docstring path example

Verification

• Python compile warning scan for the changed files reports TOTAL 0 for each file
• AST comparison against origin/master reports AST_EQUAL True for the two licensing helpers
• executable AST comparison with docstrings stripped reports AST_EQUAL_NO_DOCS True for all three changed files
• git diff --check
• git ls-files --eol tools/licensing/apachize.py tools/licensing/check.py tools/ide_exporter.py

I also checked for open duplicate PRs/issues mentioning invalid escape, SyntaxWarning, tools/licensing, apachize.py, and ide_exporter.py, and found no matches.

I did not run the full NuttX build/test suite locally because this Windows environment does not have CMake or a C compiler installed.

[github-actions]

MemBrowse Memory Report

hifive1-revb

• flash: .text -4 B (-0.0%, 83,248 B / 4,194,304 B, total: 2% used)
  No memory changes detected for:
• arduino-mega2560
• esp32-devkitc
• mirtoo
• qemu-armv8a
• qemu-intel64
• rx65n-rsk2mb
• s698pm-dkit
• stm32-nucleo-f103rb

[simbit18]

@Old-Ding Please fix

a06291a2d9 tools: escape Python string backslashes
../nuttx/tools/checkpatch.sh -c -u -m -g  8b49e46b9ee7306a463107aad643c93d5b604309..HEAD
All done! ✨ 🍰 ✨
1 file would be left unchanged.
Used config files:
    1: .codespellrc
All done! ✨ 🍰 ✨
1 file would be left unchanged.
would reformat /home/runner/work/nuttx/nuttx/nuttx/tools/licensing/check.py

Oh no! 💥 💔 💥
1 file would be reformatted.

black check failed, run following command to update the style:
  $ black <src>

Some checks failed. For contributing guidelines, see:
  https://github.com/apache/nuttx/blob/master/CONTRIBUTING.md
Error: Process completed with exit code 1.