Bp2build support for sdk_version and java_version.

This CL adds java_version and sdk_version support to bp2build
converters for
   - java library
   - java binary
   - android library
   - android binary
   - android library import

Although java import doesn't support java_version and sdk_version, the
neverlink java_library wrapper around a java_import must specify a
sdk_version when targetting a device. "none" is used by convention.

Change-Id: I22a69dea2e351858368df69ed6a703b568d613ea
Bug: 215230098
Test: Presubmits
diff --git a/bp2build/java_import_conversion_test.go b/bp2build/java_import_conversion_test.go
index a5c01cb..5661620 100644
--- a/bp2build/java_import_conversion_test.go
+++ b/bp2build/java_import_conversion_test.go
@@ -49,8 +49,9 @@
 				"jars": `["import.jar"]`,
 			}),
 			MakeBazelTarget("java_library", "example_import-neverlink", AttrNameToString{
-				"exports":   `[":example_import"]`,
-				"neverlink": `True`,
+				"exports":     `[":example_import"]`,
+				"neverlink":   `True`,
+				"sdk_version": `"none"`,
 			}),
 		}})
 }
@@ -86,8 +87,9 @@
     })`,
 			}),
 			MakeBazelTarget("java_library", "example_import-neverlink", AttrNameToString{
-				"exports":   `[":example_import"]`,
-				"neverlink": `True`,
+				"exports":     `[":example_import"]`,
+				"neverlink":   `True`,
+				"sdk_version": `"none"`,
 			}),
 		}})
 }
@@ -112,8 +114,9 @@
 				"jars": `["import.jar"]`,
 			}),
 			MakeBazelTarget("java_library", "example_import-neverlink", AttrNameToString{
-				"exports":   `[":example_import"]`,
-				"neverlink": `True`,
+				"exports":     `[":example_import"]`,
+				"neverlink":   `True`,
+				"sdk_version": `"none"`,
 			}),
 		}})
 }