impr(ci): move some kinds of tests to PR runs only (#11272)

## Problem
The pipelines after release merges are slower than they need to be at
the moment. This is because some kinds of tests/checks run on all kinds
of pipelines, even though they only matter in some of those.

## Summary of changes
Run `check-codestyle-{rust,python,jsonnet}`, `build-and-test-locally`
and `trigger-e2e-tests` only on regular PRs, not release PR or pushes to
main or release branches.

.github/workflows/_check-codestyle-rust.yml

@@ -23,8 +23,8 @@ jobs:
   check-codestyle-rust:
     strategy:
       matrix:
-        arch: ${{ fromJson(inputs.archs) }}
-    runs-on: ${{ fromJson(format('["self-hosted", "{0}"]', matrix.arch == 'arm64' && 'small-arm64' || 'small')) }}
+        arch: ${{ fromJSON(inputs.archs) }}
+    runs-on: ${{ fromJSON(format('["self-hosted", "{0}"]', matrix.arch == 'arm64' && 'small-arm64' || 'small')) }}
 
     permissions:
       packages: read