Root Config File to Control Build Test Rules Default Values (RDT-621)

[hfudev]

For now the default running targets for build & test are all defined in one place, --default-build-targets, could be more flexible with

default_rules:
  esp32: true  # build and test
  esp32h2:
    build: true
    test: false
  # test: true and build: false is invalid...
  # we skip unlisted ones, consider as build: false, test: false

if default_rules is not set, we use the same behavior as before, i.e. build & test the officially supported targets under the specified IDF_PATH.

[hfudev]

maybe also need enable_test to "whitelist" some build based on a target which has test: false by default. "blacklist" seems more intuitive.