Remove unused dependencies and disable unnecessary test targets

[aram356]

Summary

Several workspace dependencies have accumulated that are no longer used, and some crates have test/doctest targets enabled despite having no Rust tests.

Changes

Removed unused workspace dependencies:

• handlebars — no longer referenced anywhere
• pin-project-lite — removed from trusted-server-core
• tokio-test / tokio-stream — removed from dev-dependencies
• log-fastly — removed from trusted-server-core (only needed in the Fastly adapter)
• serde, serde_json, trusted-server-js — removed from trusted-server-adapter-fastly (accessed transitively via trusted-server-core)

Workspace dependency promotion:

• trusted-server-core added as a workspace dependency for consistency

Disabled unnecessary test targets:

• trusted-server-js: set test = false and doctest = false (no Rust tests, only a JS build crate)
• trusted-server-openrtb: set doctest = false

Motivation

Reduces compile times, shrinks the dependency tree, and avoids running empty test/doctest targets.