feat: resolveRoute function

[Rich-Harris]

#10282. after this is merged into master, and master is merged into version-2, we can open another PR that removes resolvePath

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[benmccann]

We could do this - though it will probably mean that people end up migrating it manually as opposed to via the migration tool and I'm not sure if we have a preference there

[Rich-Harris]

I trust deprecation warnings more than I trust automated migrations. I definitely don't think the existence of a migration tool should prevent us from providing useful feedback — there will be plenty of people who want to address deprecation warnings (possibly over a period of time) who aren't ready to bump majors

[benmccann]

I guess in this case it'd be hard to automigrate anyway since this one includes the base. I forgot for a moment that we're doing more than moving the package and renaming the function.

I didn't check if this is in the migration guide already. If it's not, we might want to include that update as part of this PR

[Rich-Harris]

If it's not, we might want to include that update as part of this PR

this is the deprecation PR. the migration instructions will be part of the removal PR