[service-manager] Introduce ServiceFilter

ServiceFilter will replace usage of Identity in APIs which take or
require only a partial Identity.

This CL adds the mojom and C++ type (with type-mapping) and updates
Connector's mojom to use ServiceFilter instead of Identity where
appropriate. Implementations of Connector are updated accordingly.

Follow-up CLs will transition callers to explicit use of ServiceFilter
and then finally change Identity to no longer have optional fields so
that all uses refer to concrete service instance identities.

Bug: 902590
Change-Id: I8587f2c7ba15a68d5d873f207ec8fa99dc0e7312
Reviewed-on: https://chromium-review.googlesource.com/c/1330895
Commit-Queue: Ken Rockot <[email protected]>
Reviewed-by: Tom Sepez <[email protected]>
Reviewed-by: Scott Violet <[email protected]>
Reviewed-by: Oksana Zhuravlova <[email protected]>
Cr-Commit-Position: refs/heads/master@{#607370}
23 files changed