bsp: Use raw regex strings in upgrade tools

[Old-Ding]

Summary

• mark heap update regex patterns as raw strings in the FT32, Infineon, and MM32 BSP upgrade tools
• keep the parsed Python AST unchanged while removing invalid escape warnings

Verification

• SyntaxWarning scan for the three changed files reports TOTAL 0
• AST comparison against origin/master reports AST_EQUAL True for all three changed files
• git diff --check
• git ls-files --eol bsp/ft32/tools/upgrade.py bsp/Infineon/tools/upgrade.py bsp/mm32/tools/upgrade.py

I also checked for open duplicate PRs/issues mentioning upgrade.py, invalid escape, SyntaxWarning, and the changed BSP tool paths, and found no matches.

[github-actions]

👋 感谢您对 RT-Thread 的贡献！Thank you for your contribution to RT-Thread!

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[github-actions]

MemBrowse Memory Report

No memory changes detected for:

• infineon-psoc6