Remove separate type_annotations artifact

And merge type_annotations in annotations. The annotations artifact is still Java 8 compatible.

The type_annotations artifact was created when annotations was Java 7-compatible, to allow using Java 8 annotation APIs (like `@Target(TYPE_USE)`).

This avoids split package issues when using Error Prone annotations from modularized builds, see e.g. #4888

Tested:
    TAP for global presubmit queue
    []
PiperOrigin-RevId: 737500755

Author: cushon

type_annotations/src/main/java/com/google/errorprone/annotations/ImmutableTypeParameter.java annotations/src/main/java/com/google/errorprone/annotations/ImmutableTypeParameter.java

@@ -49,12 +49,6 @@
       <artifactId>error_prone_annotation</artifactId>
       <version>${project.version}</version>
     </dependency>
-    <dependency>
-      <!-- Apache 2.0 -->
-      <groupId>com.google.errorprone</groupId>
-      <artifactId>error_prone_type_annotations</artifactId>
-      <version>${project.version}</version>
-    </dependency>
     <dependency>
       <!-- Apache 2.0 -->
       <groupId>com.google.errorprone</groupId>
@@ -424,7 +418,6 @@
                   <include>com.github.kevinstern:software-and-algorithms</include>
                   <include>com.google.errorprone:error_prone_annotation</include>
                   <include>com.google.errorprone:error_prone_annotations</include>
-                  <include>com.google.errorprone:error_prone_type_annotations</include>
                   <include>com.google.errorprone:error_prone_check_api</include>
                   <include>org.pcollections:pcollections</include>
                   <include>com.google.guava:guava</include>

type_annotations/src/main/java/com/google/errorprone/annotations/ThreadSafeTypeParameter.java annotations/src/main/java/com/google/errorprone/annotations/ThreadSafeTypeParameter.java

@@ -65,7 +65,6 @@
     <module>core</module>
     <module>annotation</module>
     <module>annotations</module>
-    <module>type_annotations</module>
     <module>docgen</module>
     <module>docgen_processor</module>
     <module>refaster</module>