This commit starts to lay some groundwork for the stabilization of custom
attribute invocations and general procedural macros. It applies a number of
changes discussed on [internals] as well as a [recent issue][issue], namely:

* The path used to specify a custom attribute must be of length one and cannot
  be a global path. This'll help future-proof us against any ambiguities and
  give us more time to settle the precise syntax. In the meantime though a bare
  identifier can be used and imported to invoke a custom attribute macro. A new
  feature gate, `proc_macro_path_invoc`, was added to gate multi-segment paths
  and absolute paths.

* The set of items which can be annotated by a custom procedural attribute has
  been restricted. Statements, expressions, and modules are disallowed behind
  two new feature gates: `proc_macro_expr` and `proc_macro_mod`.

* The input to procedural macro attributes has been restricted and adjusted.
  Today an invocation like `#[foo(bar)]` will receive `(bar)` as the input token
  stream, but after this PR it will only receive `bar` (the delimiters were
  removed). Invocations like `#[foo]` are still allowed and will be invoked in
  the same way as `#[foo()]`. This is a **breaking change** for all nightly
  users as the syntax coming in to procedural macros will be tweaked slightly.

* Procedural macros (`foo!()` style) can only be expanded to item-like items by
  default. A separate feature gate, `proc_macro_non_items`, is required to
  expand to items like expressions, statements, etc.

Closes #50038

[internals]: https://internals.rust-lang.org/t/help-stabilize-a-subset-of-macros-2-0/7252
[issue]: https://github.com/rust-lang/rust/issues/50038

When invoking the compiler in parallel, the intermediate output of the object
files and bytecode can stomp over one another if two crates with the same name
are being compiled.

The output file is already being disambiguated with `-C extra-filename`, so this
commit alters the naming of the temporary files to also mix in the extra
filename to ensure that file names don't clash.

The output file was only being renamed based off #[crate_name], not #[crate_id]
or --crate-name. Both of these behaviors have been restored now.

When an error is encountered when writing dependencies, this presents a nicer
error rather than an ICE.

Closes #13517

Closes #11259