Revert "Reland "refactor(core): cleanup feature flags for js source i… (#19611)

…nclusion" (#19519)"

This reverts commit 28a4f3d0f5383695b1d49ccdc8b0f799a715b2c2.

This change causes failures when used outside Deno repo:
```
============================================================
Deno has panicked. This is a bug in Deno. Please report this
at https://github.com/denoland/deno/issues/new.
If you can reliably reproduce this panic, include the
reproduction steps and re-run with the RUST_BACKTRACE=1 env
var set and include the backtrace in your report.

Platform: linux x86_64
Version: 1.34.3+b37b286
Args: ["/opt/hostedtoolcache/deno/0.0.0-b37b286f7fa68d5656f7c180f6127bdc38cf2cf5/x64/deno", "test", "--doc", "--unstable", "--allow-all", "--coverage=./cov"]

thread 'main' panicked at 'called `Result::unwrap()` on an `Err` value: Failed to read "/home/runner/work/deno/deno/core/00_primordials.js"

Caused by:
    No such file or directory (os error 2)', core/runtime/jsruntime.rs:699:8
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
```

1 files changed, 2 insertions, 10 deletions

diff --git a/core/00_primordials.js b/core/00_primordials.js
index 998bfc7ab..60474e649 100644
--- a/core/00_primordials.js
+++ b/core/00_primordials.js
@@ -34,14 +34,6 @@
 "use strict";
 
 (() => {
-  // Provide bootstrap namespace
-  globalThis.__bootstrap ??= {};
-  const key = Symbol.for("00_primordials.js");
-  if (globalThis.__bootstrap[key]) {
-    return;
-  }
-  globalThis.__bootstrap[key] = true;
-
   const primordials = {};
 
   const {
@@ -305,7 +297,6 @@
     ArrayPrototypeJoin,
     ArrayPrototypeMap,
     FunctionPrototypeCall,
-    ObjectAssign,
     ObjectDefineProperty,
     ObjectFreeze,
     ObjectPrototypeIsPrototypeOf,
@@ -619,5 +610,6 @@
   ObjectSetPrototypeOf(primordials, null);
   ObjectFreeze(primordials);
 
-  ObjectAssign(globalThis.__bootstrap, { primordials });
+  // Provide bootstrap namespace
+  globalThis.__bootstrap = { primordials };
 })();