harmony: remove special casing in routes.go

Now that we have a built-in parser abstraction, which was introduced in
<https://github.com/ollama/ollama/pull/12248>, we can modify our harmony
parser to match this and then get rid of nearly all of the
harmony-specific logic in routes.go. We do have a small amount of
code that turns the parser on by default if the architecture matches and
no other built-in parser was provided.

The built-in parser interface was modified in order to handle harmony's
prefill and tool name translation requirements.

.gitignore

@@ -6,6 +6,7 @@
 dist
 build
 .cache
+.gocache
 *.exe
 .idea
 test_data