Add custom Error Prone check for SDK comparisons.

Over the years we've had several obscure bugs related to how SDK level
comparisons are performed, specifically during the window of time
where we've started distributing the "frankenbuild" to developers.

Consider the case where a framework developer shipping release "R"
wants to only grant a specific behavior to modern apps; they could
write this in two different ways:

1. if (targetSdkVersion > Build.VERSION_CODES.Q) {
2. if (targetSdkVersion >= Build.VERSION_CODES.R) {

The safer of these two options is (2), which will ensure that
developers only get the behavior when *both* the app and the
platform concur on the specific SDK level having shipped.

Consider the breakage that would happen with option (1) if we
started shipping APKs that are based on the final R SDK, but are
then installed on earlier preview releases which still consider R
to be CUR_DEVELOPMENT; they'd risk crashing due to behaviors that
were never part of the official R SDK.

Bug: 64412239
Test: ./build/soong/soong_ui.bash --make-mode services RUN_ERROR_PRONE=true
Exempt-From-Owner-Approval: trivial blueprint changes
Change-Id: Ia20181f8602451ac9a719ea488d148e160708592