Refactor hostingType/hostingName/hostingNameStr.

These are parameters to various startProcess calls, and have been
overloaded to mean different things. In most cases, the hostingType
describes why we asked to start the process, or what type of component
we were starting it for; examples: "content provider", "service". But,
it is also used to indicate that a process should use either the Webview
or Application zygote, eg "webview_zygote". In some cases (eg for the
system process), it can be null.

The hostingName parameter is a ComponentName, which is the component we
are intending to host in the process. There are also instances where we
take a String instead of a ComponentName. This parameter is actually
only used for logging purposes, and doesn't really have any functional
effects.

To that end, introduce a new HostingRecord class to be used in the
startProcess() calls, which replaces the previous
hostingType/hostingName/hostingNameStr paramaters.

It removes the "zygote" overload and makes that explicit, and directly
converts the ComponentName to a String (since that is the only
representation of it that is used anyway).

The main reason to do this refactor now is that we need to have some
more information when starting a process for a BIND_EXTERNAL service
that use the application zygote; adding yet another parameter to
startProcess() didn't seem like the right way to go.

In the future, more information can be moved into this class, in order
to clean up the startProcess(...) calls, which have become rather
complicated.

Bug: 127820394
Test: Device boots
Change-Id: I6569bb4533ea829071e8715b7f22df918009dd08