[infra] Add nci variant and enable it on fyi bots

The native context independent (NCI) code variant will be used to test
various aspects as the NCI implementation progresses. Examples:

- Test js-generic-lowering with feedback collection.
- Test NCI codegen without caching or tier-up.
- Test NCI codegen and tier-up without caching.
- Test full NCI (codegen, caching, tier-up).

At some point a build-time flag may be required, we'll see when we get
there.

This variant should be removed once work on NCI is complete.

Bug: v8:8888
Change-Id: I8b12c9a5d69bf167e39e002af385f8f523585550
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2198776
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Auto-Submit: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#67767}

infra/testing/builders.pyl

@@ -312,6 +312,8 @@
     'tests': [
       # Infra staging.
       {'name': 'v8testing', 'variant': 'infra_staging', 'shards': 2},
+      # Native context independent code.
+      {'name': 'v8testing', 'variant': 'nci'},
       # Stress sampling.
       {'name': 'mjsunit', 'variant': 'stress_sampling'},
       {'name': 'webkit', 'variant': 'stress_sampling'},
@@ -960,6 +962,8 @@
     'tests': [
       # Infra staging.
       {'name': 'v8testing', 'variant': 'infra_staging', 'shards': 2},
+      # Native context independent code.
+      {'name': 'v8testing', 'variant': 'nci'},
       # Stress sampling.
       {'name': 'mjsunit', 'variant': 'stress_sampling'},
       {'name': 'webkit', 'variant': 'stress_sampling'},
@@ -987,6 +991,8 @@
     'tests': [
       # Infra staging.
       {'name': 'v8testing', 'variant': 'infra_staging'},
+      # Native context independent code.
+      {'name': 'v8testing', 'variant': 'nci'},
       # Stress sampling.
       {'name': 'mjsunit', 'variant': 'stress_sampling'},
       {'name': 'webkit', 'variant': 'stress_sampling'},

tools/testrunner/local/variants.py

@@ -14,6 +14,7 @@ ALL_VARIANT_FLAGS = {
   "interpreted_regexp": [["--regexp-interpret-all"]],
   "jitless": [["--jitless"]],
   "minor_mc": [["--minor-mc"]],
+  "nci": [["--turbo-nci"]],
   "no_lfa": [["--no-lazy-feedback-allocation"]],
   # No optimization means disable all optimizations. OptimizeFunctionOnNextCall
   # would not force optimization too. It turns into a Nop. Please see