Fix typecheck foundations (#167060)

## Summary
This PR is the core part of #166813. The original work seems to grow
large, and we'd like to enable a preventive check beforehand to prevent
more errors from entering the codebase.

The idea is to have a selective type check that would only check changed
files' projects.
- [x] when there's no extra label, run the selective type check only on
the diffing files' projects (success:
https://buildkite.com/elastic/kibana-pull-request/builds/161837)
- [x] when the label `ci:hard-typecheck` is present, run the regular
(but now, working) full typecheck (expected to fail: )

cc: @watson

---------

Co-authored-by: Brad White <brad.white@elastic.co>
Co-authored-by: Thomas Watson <w@tson.dk>
Co-authored-by: Thomas Watson <watson@elastic.co>
Co-authored-by: Kibana Machine <42973632+kibanamachine@users.noreply.github.com>

.buildkite/scripts/pipelines/pull_request/pipeline.ts

@@ -59,6 +59,12 @@ const uploadPipeline = (pipelineContent: string | object) => {
       pipeline.push(getPipeline('.buildkite/pipelines/pull_request/kbn_handlebars.yml'));
     }
 
+    if (GITHUB_PR_LABELS.includes('ci:hard-typecheck')) {
+      pipeline.push(getPipeline('.buildkite/pipelines/pull_request/type_check.yml'));
+    } else {
+      pipeline.push(getPipeline('.buildkite/pipelines/pull_request/type_check_selective.yml'));
+    }
+
     if (
       (await doAnyChangesMatch([
         /^src\/plugins\/controls/,

.buildkite/scripts/steps/build_api_docs.sh

@@ -4,8 +4,9 @@ set -euo pipefail
 
 .buildkite/scripts/bootstrap.sh
 
-echo "--- Run scripts/type_check to ensure that all build available"
-node scripts/type_check
+# TODO: Enable in #166813 after fixing types
+# echo "--- Run scripts/type_check to ensure that all build available"
+# node scripts/type_check
 
 echo "--- Build API Docs"
 node --max-old-space-size=12000 scripts/build_api_docs

.buildkite/scripts/steps/check_types_commits.sh

@@ -0,0 +1,114 @@
+#!/usr/bin/env bash
+
+set -euo pipefail
+
+
+if [[ "${CI-}" == "true" ]]; then
+  .buildkite/scripts/bootstrap.sh
+  
+  sha1="${GITHUB_PR_TARGET_BRANCH-}"
+  sha2="${GITHUB_PR_TRIGGERED_SHA-}"
+else
+  # Script take between 0 and 2 arguments representing two commit SHA's:
+  # If 0, it will diff HEAD and HEAD^
+  # If 1 (SHA1), it will diff SHA1 and SHA1^
+  # If 2 (SHA1, SHA2), it will diff SHA1 and SHA2
+  sha1="${1-HEAD}"
+  sha2="${2-$sha1^}"
+fi
+
+uniq_dirs=()
+uniq_tsconfigs=()
+
+echo "Detecting files changed between $sha1 and $sha2..."
+
+files=($(git diff --name-only $sha1 $sha2))
+
+add_dir () {
+  new_dir=$1
+
+  if [ ${#uniq_dirs[@]} -gt 0 ]; then
+    for dir in "${uniq_dirs[@]}"
+    do
+      if [[ "$new_dir" == "$dir" ]]; then
+        return
+      fi
+    done
+  fi
+
+  uniq_dirs+=($new_dir)
+}
+
+add_tsconfig () {
+  new_tsconfig=$1
+
+  if [ ${#uniq_tsconfigs[@]} -gt 0 ]; then
+    for tsconfig in "${uniq_tsconfigs[@]}"
+    do
+      if [[ "$new_tsconfig" == "$tsconfig" ]]; then
+        return
+      fi
+    done
+  fi
+
+  echo "  $new_tsconfig"
+  uniq_tsconfigs+=($new_tsconfig)
+}
+
+contains_tsconfig () {
+  dir=$1
+  tsconfig="$dir/tsconfig.json"
+  if [ -f "$tsconfig" ]; then
+    true
+  else
+    false
+  fi
+}
+
+find_tsconfig () {
+  dir=$1
+
+  if [[ "$dir" == "." ]]; then
+    return
+  fi
+
+  if contains_tsconfig $dir; then
+    add_tsconfig "$dir/tsconfig.json"
+  else
+    find_tsconfig $(dirname -- "$dir")
+  fi
+}
+
+if [ ${#files[@]} -eq 0 ]; then
+  echo "No files found!"
+  exit
+fi
+
+for file in "${files[@]}"
+do
+  dir=$(dirname -- "$file")
+
+  # Ignore buildkite dir because it traverses many kbn packages and emits incorrect results
+  if [[ "$dir" != .buildkite* ]]; then
+    add_dir $dir
+  fi
+done
+
+echo "Looking for related tsconfig.json files..."
+
+for dir in "${uniq_dirs[@]}"
+do
+  find_tsconfig $dir
+done
+
+if [ ${#uniq_tsconfigs[@]} -eq 0 ]; then
+  echo "No tsconfig.json files found for changes in $sha1 $sha2"
+  exit
+fi
+
+echo "Running scripts/type_check for each found tsconfig.json file..."
+
+for tsconfig in "${uniq_tsconfigs[@]}"
+do
+  node scripts/type_check --project $tsconfig
+done