Remove ApexBundleDepsInfo.MinSdkVersion()

For java.AndroidApp app, app.MinSdkVersion() was selected from
ApexBundleDepsInfo, not from java.Module.
This caused app.MinSdkVersion() to return "" always.

Besides, having two embeded fields and relying on depth to choose one of
them makes it hard to read.

Bug: 156537348
Test: m
Merged-In: Ib525b2f5132c596db8e33492d0a565ea23e91d1c
Change-Id: Ib525b2f5132c596db8e33492d0a565ea23e91d1c
Exempt-From-Owner-Approval: cp from aosp
(cherry picked from commit 98d63e1c)