refactor(core): include_js_files! 'dir' option doesn't change specifiers (#18019)

This commit changes "include_js_files!" macro from "deno_core"
in a way that "dir" option doesn't cause specifiers to be rewritten 
to include it.

Example:
```
include_js_files! {
  dir "js",
  "hello.js",
}
```

The above definition required embedders to use:
`import ... from "internal:<ext_name>/js/hello.js"`. 
But with this change, the "js" directory in which the files are stored
is an implementation detail, which for embedders results in: 
`import ... from "internal:<ext_name>/hello.js"`.

The directory the files are stored in, is an implementation detail and 
in some cases might result in a significant size difference for the 
snapshot. As an example, in "deno_node" extension, we store the 
source code in "polyfills" directory; which resulted in each specifier 
to look like "internal:deno_node/polyfills/<module_name>", but with 
this change it's "internal:deno_node/<module_name>". 

Given that "deno_node" has over 100 files, many of them having 
several import specifiers to the same extension, this change removes
10 characters from each import specifier.

1 files changed, 1 insertions, 1 deletions

diff --git a/ext/node/polyfills/internal_binding/_timingSafeEqual.ts b/ext/node/polyfills/internal_binding/_timingSafeEqual.ts
index 9002300d1..a1cc093d6 100644
--- a/ext/node/polyfills/internal_binding/_timingSafeEqual.ts
+++ b/ext/node/polyfills/internal_binding/_timingSafeEqual.ts
@@ -1,5 +1,5 @@
 // Copyright 2018-2023 the Deno authors. All rights reserved. MIT license.
-import { Buffer } from "internal:deno_node/polyfills/buffer.ts";
+import { Buffer } from "internal:deno_node/buffer.ts";
 
 function assert(cond) {
   if (!cond) {