Limit System SDK to 34 for Java modules in the vendor partition

This change disallows Java modules in the vendor partition to use System
SDK that is newer than API level 34; 34 is the latest allowed.

Background 1: with Trunk Stable, the system/vendor interface is released
at Q2 whereas the system/app interface is released at Q3. In other
words, at Q2, the APIs which will be added to the system SDK at Q3 are
not available. Since the system/vendor interface (which is fronzen at
Q2) is what the modules in the vendor partition will be building
against, they can't and shouldn't use those new APIs that will be added
in the future (Q3). Using those APIs is risky because there's a chance
that those APIs get removed or changed between Q2 and Q3. For example,
2024 Q2 is technically still Android U, not Android V.

Background 2: The use of Java APIs in the vendor partition had many
issues. Most significantly, those "vendor" Java apps are categorized as
part of the system partition because all Java app processes require
access to platform internal libraries that are prohibited to vendor
processes. Furthermore, since the Project Treble, the vendor partition
was re-purposed to a partition to host SoC-dependent bits - usually
HALs. Implementing HALs in Java has never been officially supported and
has had many loop holes.

We'd like to use both background 1 and 2 as a chance to disallow any
Java code in the vendor partition. However, since there are already some
Java modules in the partition, we can't suddenly ban it. The deprecation
will be made gradually, and this CL is the start.

Note that sdk_version: "current" or "system_current" is automatically
overridden into 34 or system_34. This is to prevent sudden breakage of
vendor modules that have been targetting the latest (i.e. current) API
level. They will however fail if they use APIs newer than API level 34.

Bug: 314011075
Test: m blueprint_tests
Change-Id: I59f5ac15ce9ac2ff7cc89e9c110169359077c37c