[cobalt] Remove EncoderFactory from svchost and cleanup

The EncoderFactory FIDL service has been removed. Also removes a couple
of remaining references to the "Encoder"

Test: compiles
Change-Id: I89495c8d3d29d339181d48b8a0e96550d6e0b6f7

[cobalt] Reland FIDL readability changes

This is a reland of 75f022dfd0c35f73385edd22610273a2562559d3

Original change's description:
> [cobalt] Update API to comply with FIDL readability
>
> Tested: Verified existing CQ tests pass.
> Change-Id: I284d6aa90894a176d279f8a3e3efbf9ebfb47d14

Change-Id: Ia12d408024027d5bb9386a9a1077c2f7575dcfd6

Revert "[cobalt] Update API to comply with FIDL readability"

This reverts commit 75f022dfd0c35f73385edd22610273a2562559d3.

Reason for revert: Unblock the rollers while debugging a failure with landing the Garnet portion of this change

Original change's description:
> [cobalt] Update API to comply with FIDL readability
>
> Tested: Verified existing CQ tests pass.
> Change-Id: I284d6aa90894a176d279f8a3e3efbf9ebfb47d14

TBR=rudominer@google.com,abarth@google.com,jsankey@google.com

Change-Id: I0ae8a08cbd2bbfdf97cda0e1854da23331b7a85a
No-Presubmit: true
No-Tree-Checks: true
No-Try: true

[cobalt] Update API to comply with FIDL readability

Tested: Verified existing CQ tests pass.
Change-Id: I284d6aa90894a176d279f8a3e3efbf9ebfb47d14

[fidl] Rename FIDL directories

These names more closely match what we publish in the SDK. Ideally, we'd
use . as the separator, but Zircon's build system cannot handle . in
directory names, so we use - instead.

Test: Builds.
Change-Id: Ia420a364d2accac39faebade8f3f8ed72088556a