Always separate type arguments with a space

Preparation for adding support for record and sealed classes.

Previously, the separation of type arguments was inconsistent depending
on where the type was used.

This change fixes that by setting `type-argument-spacing=space` which
will separate them with a space separator everywhere.

FCRS_CODE: sdkExempt
Flag: EXEMPT PURE_REFACTOR
Bug: 493237547
API-Coverage-Bug: 493237547
Test: m checkapi

Change-Id: I3533455a61b5785b9bcf010ce8d07aea2bb892e0