Rework CI workflows (#8688)

- split workflows into separate files to trigger by path
  this should help out documentation and boards / eboot / pkg files
  updates, since those *wont* trigger usual build stuff anymore
- build*.sh whatever merged into just common.sh and build.sh
  trigger different parity builds, mod % rem and allow to set .ino list
  through the environment variable
- removes unnecessary temporary files, try to use more pipes
  move remaining ones into cache dir instead of PWD
- remove legacy TRAVIS env vars, use ESP8266_ARDUINO prefix for config
- remove Windows path workarounds
- hardware/ and ide/ directories are set through envionment
  do not force specific paths, simplify builds on local machine
- sketch list is set through environment. expicit paths for Windows and
  macOS builders. platformio also gets a real shuffled list instead of
  mod and rem magic numbers
- detect root of the repo through git cli, not base{name,dir} or relative paths

tests/ci/build_boards.sh

@@ -4,11 +4,14 @@
 
 set -ev
 
-cd $TRAVIS_BUILD_DIR
+root=$(git rev-parse --show-toplevel)
 
+cd $root
 tools/boards.txt.py --boardsgen --ldgen --packagegen --docgen
 
-git diff --exit-code -- boards.txt \
-                        doc/boards.rst \
-                        tools/sdk/ld/
-git diff --exit-code -w -- package/package_esp8266com_index.template.json
+git diff --exit-code -- \
+    boards.txt \
+    doc/boards.rst \
+    tools/sdk/ld/
+git diff --exit-code --ignore-all-space -- \
+    package/package_esp8266com_index.template.json