Bump to Bazel 8.0.0rc6, fix //third_party tests

Fixes `{strict_deps,unused_dependency_checker}_test` from
`//third_party/dependency_analyzer/src/test` by updating `$(location)`
to `$(rootpath)`. Part of bazelbuild#1652.

`//third_party/dependency_analyzer/src/test:strict_deps_test` and
`//third_party/dependency_analyzer/src/test:unused_dependency_checker_test`
both failed with errors of the form:

```txt
StrictDepsTest:
- error on indirect dependency target *** FAILED *** (379 milliseconds)
  nice errors on sequence of strings.this.infos.exists(nice errors on
  sequence of strings.this.checkErrorContainsMessage(target)) was false
  expected an error on //commons:Target to appear in errors (with
  buildozer command)!
  Errors: List(object apache is not a member of package org)
  (StrictDepsTest.scala:85)
```

This happened both under `WORKSPACE` and Bzlmod.

These targets both depend on
`@org_apache_commons_commons_lang_3_5_without_file//:linkable_org_apache_commons_commons_lang_3_5_without_file`.
The `@org_apache_commons_commons_lang_3_5_without_file` repo is now
instantiated by `dev_deps_repositories()` from
`scala/private/extensions/dev_deps.bzl`. These tests pass on Bazel 6 and
7.

I added code to the "error on indirect dependency target" test case
from `third_party/dependency_analyzer/src/test/io/bazel/rulesscala/
dependencyanalyzer/StrictDepsTest.scala` to see the result of
`compileWithDependencyAnalyzer()`:

```diff
diff --git a/third_party/dependency_analyzer/src/test/io/bazel/rulesscala/dependencyanalyzer/StrictDepsTest.scala b/third_party/dependency_analyzer/src/test/io/bazel/rulesscala/dependencyanalyzer/StrictDepsTest.scala
index b26ba5e5..76b19e90 100644
--- a/third_party/dependency_analyzer/src/test/io/bazel/rulesscala/dependencyanalyzer/StrictDepsTest.scala
+++ b/third_party/dependency_analyzer/src/test/io/bazel/rulesscala/dependencyanalyzer/StrictDepsTest.scala
@@ -37,7 +37,9 @@ class StrictDepsTest extends AnyFunSuite {
     val commonsTarget = "//commons:Target"

     val indirect = List(apacheCommonsClasspath -> commonsTarget)
-    compileWithDependencyAnalyzer(testCode, withIndirect = indirect).expectErrorOn(commonsTarget)
+    val errors = compileWithDependencyAnalyzer(testCode, withIndirect = indirect)
+    System.out.println(errors)
+    errors.expectErrorOn(commonsTarget)
   }

   test("error on multiple indirect dependency targets") {
```

Under Bazel 7.4.1, the test passed and shows this output:

```txt
$ bazel test --test_output=streamed \
  //third_party/dependency_analyzer/src/test:strict_deps_test

[ ...snip... ]
StrictDepsTest:
List(Target '//commons:Target' is used but isn't explicitly declared, please add it to the deps.
You can use the following buildozer command:
buildozer 'add deps //commons:Target' //...)
```

Under Bazel 8.0.0rc6, it failed and showed this:

```txt
$ bazel test --test_output=streamed \
  //third_party/dependency_analyzer/src/test:strict_deps_test

[ ...snip... ]
StrictDepsTest:
List(object apache is not a member of package org)
```

.bazelversion

@@ -1 +1 @@
-7.4.1
+8.0.0rc6

dt_patches/compiler_sources/.bazelversion

@@ -1 +1 @@
-7.4.1
+8.0.0rc6

dt_patches/test_dt_patches/.bazelversion

@@ -1 +1 @@
-7.4.1
+8.0.0rc6

dt_patches/test_dt_patches_user_srcjar/.bazelversion

@@ -1 +1 @@
-7.4.1
+8.0.0rc6

examples/crossbuild/.bazelversion

@@ -1 +1 @@
-7.4.1
+8.0.0rc6

examples/scala3/.bazelversion

@@ -1 +1 @@
-7.4.1
+8.0.0rc6

examples/semanticdb/.bazelversion

@@ -1 +1 @@
-7.4.1
+8.0.0rc6

examples/testing/multi_frameworks_toolchain/.bazelversion

@@ -1 +1 @@
-7.4.1
+8.0.0rc6

examples/testing/scalatest_repositories/.bazelversion

@@ -1 +1 @@
-7.4.1
+8.0.0rc6

examples/testing/specs2_junit_repositories/.bazelversion

@@ -1 +1 @@
-7.4.1
+8.0.0rc6

test/proto_cross_repo_boundary/repo/.bazelversion

@@ -1 +1 @@
-7.4.1
+8.0.0rc6

test_cross_build/.bazelversion

@@ -1 +1 @@
-7.4.1
+8.0.0rc6

third_party/dependency_analyzer/src/test/analyzer_test.bzl

@@ -61,7 +61,7 @@ def tests():
         ],
         jvm_flags = common_jvm_flags + [
             "-Dguava.jar.location=$(rootpath @com_google_guava_guava_21_0_with_file//jar)",
-            "-Dapache.commons.jar.location=$(location @org_apache_commons_commons_lang_3_5_without_file//:linkable_org_apache_commons_commons_lang_3_5_without_file)",
+            "-Dapache.commons.jar.location=$(rootpath @org_apache_commons_commons_lang_3_5_without_file//:linkable_org_apache_commons_commons_lang_3_5_without_file)",
         ],
         unused_dependency_checker_mode = "off",
         deps = scala_std_dependencies + [
@@ -80,7 +80,7 @@ def tests():
             "io/bazel/rulesscala/dependencyanalyzer/UnusedDependencyCheckerTest.scala",
         ],
         jvm_flags = common_jvm_flags + [
-            "-Dapache.commons.jar.location=$(location @org_apache_commons_commons_lang_3_5_without_file//:linkable_org_apache_commons_commons_lang_3_5_without_file)",
+            "-Dapache.commons.jar.location=$(rootpath @org_apache_commons_commons_lang_3_5_without_file//:linkable_org_apache_commons_commons_lang_3_5_without_file)",
         ],
         unused_dependency_checker_mode = "off",
         deps = scala_std_dependencies + [

third_party/test/example_external_workspace/.bazelversion

@@ -1 +1 @@
-7.4.1
+8.0.0rc6

third_party/test/new_local_repo/.bazelversion

@@ -1 +1 @@
-7.4.1
+8.0.0rc6

third_party/test/proto/.bazelversion

@@ -1 +1 @@
-7.4.1
+8.0.0rc6