Initial implementation of bug report dump

The first iteration is to mimic adb shell devic_config list command
output. Future designs are being debated and reasoned. The future design
would improve in the following categories:

(1) differentiate legacy flags and aconfig flags, and have two seperate
print out sections
(2) for aconfig flags, it will be sorted by feature name, or aconfig
package name

Bug: b/289197050
Test: adb shell dumpsys device_config
Change-Id: I1b70ef2ec03aaeefa64b05173a2fbbb668979705