Prepare role code for modularization.

- PooledLambda: PoolLambda is replaced with plain lambdas, to avoid
adding ~20 classes to boot classpath (for each module that uses
lambda).

- SystemServiceRegistry: RoleFrameworkInitializer is added to add
ROLE_SERVICE, similar to other modules.

- RoleService: RoleManagerService is renamed to RoleService to better
reflect the manager/service relationship.

- @MainThread: import for Looper is removed because it's only used in
javadoc and triggers package not exist error during build. @linkplain
in the javadoc is also removed because it triggers an error in
Metalava parsing and isn't critical.

- Added small utilities: These utilities has their full version in
platform, but is too large and contains too many internal references
in methods unreferenced by role, whereas actually role only needs 1 or
2 methods from them. So just create a small copy of the used methods
for role modularization, and they will be moved into APEX with role.

Bug: 158736025
Test: manual
Change-Id: I74f20b37d23370e258e7fc7130e28c5312abf46c