Upgrade Rust to 1.78.0.

The 1.78 release bumps the minimum supported Windows version to Windows
10; so we bump our major version to indicate the breaking change, and,
~1.5 years after the first public release, semi-offcially declare
stability given some level of battle testing.

As a point of reference, Microsoft support for Windows 8 ended on
January 12, 2016, and support for Windows 8.1 ended on
January 10, 2023; so `ptex` likely only ever could have had Windows 8.1
users.

The release announcement is here:
  https://blog.rust-lang.org/2024/05/02/Rust-1.78.0.html

.circleci/config.yml

@@ -46,7 +46,7 @@ jobs:
             docker run --rm \
               -v $PWD:/code \
               -w /code \
-              rust:1.77.2-alpine3.19 \
+              rust:1.78.0-alpine3.19 \
                 sh -c 'apk add cmake make musl-dev perl && cargo run -p package -- dist'
       - persist_to_workspace:
           root: dist

.github/workflows/ci.yml

@@ -48,5 +48,5 @@ jobs:
           docker run --rm \
             -v $PWD:/code \
             -w /code \
-            rust:1.77.2-alpine3.19 \
+            rust:1.78.0-alpine3.19 \
               sh -c 'apk add cmake make musl-dev perl && cargo run -p package -- dist'

.github/workflows/release.yml

@@ -64,7 +64,7 @@ jobs:
           docker run --rm \
             -v $PWD:/code \
             -w /code \
-            rust:1.77.2-alpine3.19 \
+            rust:1.78.0-alpine3.19 \
               sh -c 'apk add cmake make musl-dev perl && cargo run -p package -- dist'
       - name: Prepare Changelog
         id: prepare-changelog

rust-toolchain

@@ -2,7 +2,7 @@
 # N.B.: Update .github and .circleci yaml to use a matching image, if available.
 # Although a version match is not required (cargo downloads and installs the
 # toolchain described here if not present), it does speed up CI builds.
-channel = "1.77.2"
+channel = "1.78.0"
 components = [
   "cargo",
   "clippy",