[oldergod]

This adds encodeInTagOrder to the kotlin {} and java {} targets.
It is false by default.

With the option on, the generated encode functions write fields in ascending tag order.
The bytes are then the same as protoc.
This includes oneof fields and extension fields.
In Kotlin, a boxed or sealed oneof splits around plain fields that have tags between its members.

With the option off, the generated code does not change.

The option applies only to the types that the target generates.
A nested type that another module or jar generates keeps its own field order.

You cannot use compact and encodeInTagOrder together on a java {} target, because compact code encodes by reflection.
The Gradle plugin fails before code generation when both are set.

Closes #3746.

Release note:

• New: encodeInTagOrder option on the kotlin {} and java {} targets. When it is true, the generated encode functions write fields in ascending tag order, so the bytes are the same as protoc. It is false by default, and generated code does not change when it is false (Add an option to encode fields in tag order #3751)
• Binary change: the constructors and copy functions of KotlinTarget and JavaTarget, the constructors of KotlinSchemaHandler and JavaSchemaHandler, and KotlinGenerator.invoke have a new last parameter encodeInTagOrder with the default value false. Kotlin source that calls them compiles without change. Java source that calls them must add the new argument. Code that is compiled against an earlier Wire version and calls them directly must be compiled again (Add an option to encode fields in tag order #3751)