Include SDK extensions data in bugreports

derive_sdk is used to configure installed SDK extensions. It can also
print debug information about these.

Teach dumpstate to call derive_sdk.

Also include ro.build.version.sdk (the version of the platform SDK) in
the bugreport header.

Bug: 240656777
Test: adb bugreport /tmp/bugreport.zip && unzip -c /tmp/bugreport.zip bugreport*.txt | grep -i 'sdk extensions'
Change-Id: I025244aa7ae6dec23f0f6773e24394d722ff7dba