Add inactive buildvariant for running tests against latest server

Author: jamis

.evergreen/config.yml

@@ -777,6 +777,10 @@ axes:
   - id: "mongodb-version"
     display_name: MongoDB Version
     values:
+      - id: 'latest'
+        display_name: 'Latest'
+        variables:
+          MONGODB_VERSION: 'latest'
       - id: "8.0"
         display_name: "8.0"
         variables:
@@ -1571,6 +1575,19 @@ buildvariants:
 #    tasks:
 #      - name: "test-fle"
 
+  - name: 'latest'
+    activate: false
+    display_name: 'Latest MongoDB'
+    run_on: ubuntu2404-small
+    expansions:
+      FLE: helper
+      TOPOLOGY: replica_set
+      MLAUNCH_TOPOLOGY: replica-set
+      RVM_RUBY: "ruby-4.0"
+      MONGODB_VERSION: 'latest'
+    tasks:
+      - name: "test-fle"
+
   - matrix_name: aws-auth-regular
     matrix_spec:
       # https://jira.mongodb.org/browse/RUBY-3311

.evergreen/config/axes.yml.erb

@@ -2,6 +2,10 @@ axes:
   - id: "mongodb-version"
     display_name: MongoDB Version
     values:
+      - id: 'latest'
+        display_name: 'Latest'
+        variables:
+          MONGODB_VERSION: 'latest'
       - id: "8.0"
         display_name: "8.0"
         variables:

.evergreen/config/standard.yml.erb

@@ -29,7 +29,6 @@
   # The latest stable version of MongoDB
   latest_stable_mdb = "8.0".inspect # so it gets quoted as a string
 
-
   recent_mdb = %w( 8.0 7.0 )
 %>
 
@@ -379,6 +378,19 @@ buildvariants:
 #    tasks:
 #      - name: "test-fle"
 
+  - name: 'latest'
+    activate: false
+    display_name: 'Latest MongoDB'
+    run_on: ubuntu2404-small
+    expansions:
+      FLE: helper
+      TOPOLOGY: replica_set
+      MLAUNCH_TOPOLOGY: replica-set
+      RVM_RUBY: <%= latest_ruby %>
+      MONGODB_VERSION: 'latest'
+    tasks:
+      - name: "test-fle"
+
   - matrix_name: aws-auth-regular
     matrix_spec:
       # https://jira.mongodb.org/browse/RUBY-3311