Add use-counter and WebDX feature mapping for calc-constants.

There are no clear WPT tests for e/pi (e.g. pi is only used inside
the sin-cos-tan tests), so we don't add a WPT mapping for them.

Change-Id: I36fe37239bcb5c1b28c9835a2c5c3c2cd08cbcfb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6000633
Reviewed-by: Shunya Shishido <[email protected]>
Commit-Queue: Steinar H Gunderson <[email protected]>
Reviewed-by: Daniil Sakhapov <[email protected]>
Cr-Commit-Position: refs/heads/main@{#1379608}

css/css-values/WEB_FEATURES.yml

@@ -32,3 +32,6 @@ features:
   files:
   - acos-asin-atan-atan2-*
   - sin-cos-tan-*
+- name: calc-constants
+  files:
+  - calc-infinity-*