docs(ref): Have workspace docs link out to patch/replace docs

The workspace behavior doesn't seem to be documented at all, so a blurb
was brought in that is like the profile blurb.  The workspace docs then
link out to it so users can be aware of this special workspace behavior.

Author: epage

src/doc/src/reference/overriding-dependencies.md

@@ -291,6 +291,10 @@ also be patched with versions of crates that already exist. If a source is
 patched with a crate version that already exists in the source, then the
 source's original crate is replaced.
 
+Cargo only looks at the patch settings in the `Cargo.toml` manifest at the
+root of the workspace. Patch settings defined in dependencies will be
+ignored.
+
 ### The `[replace]` section
 
 > **Note**: `[replace]` is deprecated. You should use the
@@ -313,6 +317,10 @@ dependencies, except that you can't specify features. Note that when a crate
 is overridden the copy it's overridden with must have both the same name and
 version, but it can come from a different source (e.g., git or a local path).
 
+Cargo only looks at the replace settings in the `Cargo.toml` manifest at the
+root of the workspace. Replace settings defined in dependencies will be
+ignored.
+
 ### `paths` overrides
 
 Sometimes you're only temporarily working on a crate and you don't want to have

src/doc/src/reference/workspaces.md

@@ -25,6 +25,8 @@ In the `Cargo.toml`, the `[workspace]` table supports the following sections:
   * [`metadata`](#the-metadata-table) — Extra settings for external tools.
   * [`package`](#the-package-table) — Keys for inheriting in packages.
   * [`dependencies`](#the-dependencies-table) — Keys for inheriting in package dependencies.
+* [`[patch]`](overriding-dependencies.md#the-patch-section) — Override dependencies.
+* [`[replace]`](overriding-dependencies.md#the-replace-section) — Override dependencies (deprecated).
 * [`[profile]`](profiles.md) — Compiler settings and optimizations.
 
 ### The `[workspace]` section