Make GetDirectDep implementation match comment

The comment on the interface of GetDirectDep states if there are
multiple deps with different tags, the first will be returned; however,
the current behavior is to panic if there are multiple deps. The
behavior now:
* a single dep, return the module and tag
* a single module with different tags: return module with first tag
* multiple modules: panic
* no module: return nil, nil

Bug: 186488405
Test: ~/aosp/build/bazel/ci/bp2build.sh
Test: m nothing
Change-Id: Id1e7315e7874b4a683ad7357ed2793822315821f

bp2build/cc_library_static_conversion_test.go

@@ -719,6 +719,31 @@ cc_library_static {
             "not-for-x86_64.c",
         ],
     }),
+)`},
+		},
+		{
+			description:                        "cc_library_static multiple dep same name panic",
+			moduleTypeUnderTest:                "cc_library_static",
+			moduleTypeUnderTestFactory:         cc.LibraryStaticFactory,
+			moduleTypeUnderTestBp2BuildMutator: cc.CcLibraryStaticBp2Build,
+			depsMutators:                       []android.RegisterMutatorFunc{cc.RegisterDepsBp2Build},
+			filesystem:                         map[string]string{},
+			bp: soongCcLibraryStaticPreamble + `
+cc_library_static { name: "static_dep" }
+cc_library_static {
+    name: "foo_static",
+    static_libs: ["static_dep"],
+    whole_static_libs: ["static_dep"],
+}`,
+			expectedBazelTargets: []string{`cc_library_static(
+    name = "foo_static",
+    copts = ["-I."],
+    deps = [":static_dep"],
+    linkstatic = True,
+)`, `cc_library_static(
+    name = "static_dep",
+    copts = ["-I."],
+    linkstatic = True,
 )`},
 		},
 	}