Comprehensive Rust v2 (#1073)

I've taken some work by @fw-immunant and others on the new organization
of the course and condensed it into a form amenable to a text editor and
some computational analysis. You can see the inputs in `course.py` but
the interesting bits are the output: `outline.md` and `slides.md`.

The idea is to break the course into more, smaller segments with
exercises at the ends and breaks in between. So `outline.md` lists the
segments, their duration, and sums those durations up per-day. It shows
we're about an hour too long right now! There are more details of the
segments in `slides.md`, or you can see mostly the same stuff in
`course.py`.

This now contains all of the content from the v1 course, ensuring both
that we've covered everything and that we'll have somewhere to redirect
every page.

Fixes #1082.
Fixes #1465.

---------

Co-authored-by: Nicole LeGare <dlegare.1001@gmail.com>
Co-authored-by: Martin Geisler <mgeisler@google.com>

src/std-types/exercise.rs

@@ -0,0 +1,64 @@
+// Copyright 2023 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#![allow(unused_variables, dead_code)]
+// ANCHOR: solution
+use std::collections::HashMap;
+use std::hash::Hash;
+
+/// Counter counts the number of times each value of type T has been seen.
+struct Counter<T: Eq + Hash> {
+    values: HashMap<T, u64>,
+}
+
+impl<T: Eq + Hash> Counter<T> {
+    /// Create a new Counter.
+    fn new() -> Self {
+        Counter {
+            values: HashMap::new(),
+        }
+    }
+
+    /// Count an occurrence of the given value.
+    fn count(&mut self, value: T) {
+        *self.values.entry(value).or_default() += 1;
+    }
+
+    /// Return the number of times the given value has been seen.
+    fn times_seen(&self, value: T) -> u64 {
+        self.values.get(&value).copied().unwrap_or_default()
+    }
+}
+
+// ANCHOR: main
+fn main() {
+    let mut ctr = Counter::new();
+    ctr.count(13);
+    ctr.count(14);
+    ctr.count(16);
+    ctr.count(14);
+    ctr.count(14);
+    ctr.count(11);
+
+    for i in 10..20 {
+        println!("saw {} values equal to {}", ctr.times_seen(i), i);
+    }
+
+    let mut strctr = Counter::new();
+    strctr.count("apple");
+    strctr.count("orange");
+    strctr.count("apple");
+    println!("got {} apples", strctr.times_seen("apple"));
+}
+// ANCHOR_END: main