* Move ICACHE_* to unique sections, local LD script
Similar to PROGMEM changes, make the name of each ICACHE_* variable/fuction
unique to avoid issues with section conflicts.
Also rename the generated LD linker script to avoid issue with older copies
of the eagle.app.v6.common.ld which were generated by the build process
in a global directory before being moved to the {build.path}. The linker
would use the older, generated *.ld file instead of the generated one, which
would lead to runtime failures on some systems and cause the VTABLE location
to not correspond to the IDE menu selection.
Fixes#5115, and is an update to #5117 and #5116.
* Update boards.txt.py and platform.io build