fix: allow new, subsequent `rust-project.json`-based workspaces to get proc macro expansion
As detailed in https://github.com/rust-lang/rust-analyzer/issues/14417#issuecomment-1485336174, `rust-project.json` workspaces added after the initial `rust-project.json`-based workspace was already indexed by rust-analyzer would not receive procedural macro expansion despite `config.expand_proc_macros` returning true. To fix this issue:
1. I changed `reload.rs` to check which workspaces are newly added.
2. Spawned new procedural macro expansion servers based on the _new_ workspaces.
1. This is to prevent spawning duplicate procedural macro expansion servers for already existing workspaces. While the overall memory usage of duplicate procedural macro servers is minimal, this is more about the _principle_ of not leaking processes 😅.
3. Launched procedural macro expansion if any workspaces are `rust-project.json`-based _or_ `same_workspaces` is true. `same_workspaces` being true (and reachable) indicates that that build scripts have finished building (in Cargo-based projects), while the build scripts in `rust-project.json`-based projects have _already been built_ by the build system that produced the `rust-project.json`.
I couldn't really think of structuring this code in a better way without engaging with https://github.com/rust-lang/rust-analyzer/issues/7444.
fix: Properly handle local trait impls
Before we only handled trait impls that came from the block of either the trait or the target type, we now handle them correctly by tracking the block we are currently inferring from, then walking that up to collect all block trait impls.
finish renaming `rust-analyzer/reloadProcMacros` to `rust-analyzer/rebuildProcMacros`
I was trying out #14409, but noticed that actually _running_ that command resulted in VS Code raising an error. This allows me to successfully run `rust-analyzer/rebuildProcMacros`.
internal: Only intern blocks that declare items
We only used `BlockId` for the block defmap, so this is wasted memory. Lowering for non item declaring blocks is also cheaper now as we no longer have to fully lower a block that defines not items.
