BREAKING(ffi/unstable): always return u64 as bigint (#23981)

The mixed `number | bigint` representation was useful optimization for
pointers. Now, pointers are represented as V8 externals. As part of the
FFI stabilization effort we want to make `bigint` the only
representation for `u64` and `i64`.

BigInt representation performance is almost on par with mixed
representation with the added benefit that its less confusing and users
don't need manual checks and conversions for doing operations on the
value.

```
cpu: AMD Ryzen 5 7530U with Radeon Graphics
runtime: deno 1.43.6+92a8d09 (x86_64-unknown-linux-gnu)

file:///home/divy/gh/ffi/main.ts
benchmark                 time (avg)        iter/s             (min … max)       p75       p99      p995
-------------------------------------------------------------------------- -----------------------------
nop                        4.01 ns/iter 249,533,690.5     (3.97 ns … 10.8 ns) 3.97 ns 4.36 ns 9.03 ns
ret bigint                 7.74 ns/iter 129,127,186.8    (7.72 ns … 10.46 ns) 7.72 ns 8.11 ns 8.82 ns
ret i32                    7.81 ns/iter 128,087,100.5    (7.77 ns … 12.72 ns) 7.78 ns 8.57 ns 9.75 ns
ret bigint (add op)       15.02 ns/iter  66,588,253.2   (14.64 ns … 24.99 ns) 14.76 ns 19.13 ns 19.44 ns
ret i32    (add op)       12.02 ns/iter  83,209,131.8   (11.95 ns … 18.18 ns) 11.98 ns 13.11 ns 14.5 ns
```

3 files changed, 8 insertions, 8 deletions

diff --git a/tests/ffi/tests/ffi_types.ts b/tests/ffi/tests/ffi_types.ts
index 596662873..93ac98d92 100644
--- a/tests/ffi/tests/ffi_types.ts
+++ b/tests/ffi/tests/ffi_types.ts
@@ -160,7 +160,7 @@ let r_1: number | bigint = result;
 const result2 = remote.symbols.method17();
 // @ts-expect-error: Invalid argument
 result2.then((_0: string) => {});
-result2.then((_1: number | bigint) => {});
+result2.then((_1: bigint) => {});
 
 const result3 = remote.symbols.method18();
 // @ts-expect-error: Invalid argument
@@ -430,7 +430,7 @@ type __Tests__ = [
       symbols: {
         foo: (
           ...args: (number | Deno.PointerValue | null)[]
-        ) => number | bigint;
+        ) => bigint;
       };
       close(): void;
     },
diff --git a/tests/ffi/tests/integration_tests.rs b/tests/ffi/tests/integration_tests.rs
index d0ac6e104..2235405a8 100644
--- a/tests/ffi/tests/integration_tests.rs
+++ b/tests/ffi/tests/integration_tests.rs
@@ -76,10 +76,10 @@ fn basic() {
     5\n\
     5\n\
     579\n\
-    8589934590\n\
-    -8589934590\n\
-    8589934590\n\
-    -8589934590\n\
+    8589934590n\n\
+    -8589934590n\n\
+    8589934590n\n\
+    -8589934590n\n\
     9007199254740992n\n\
     9007199254740992n\n\
     -9007199254740992n\n\
@@ -110,7 +110,7 @@ fn basic() {
     Before\n\
     After\n\
     logCallback\n\
-    1 -1 2 -2 3 -3 4 -4 0.5 -0.5 1 2 3 4 5 6 7 8\n\
+    1 -1 2 -2 3 -3 4n -4n 0.5 -0.5 1 2 3 4 5 6 7 8\n\
     u8: 8\n\
     buf: [1, 2, 3, 4, 5, 6, 7, 8]\n\
     logCallback\n\
diff --git a/tests/ffi/tests/test.js b/tests/ffi/tests/test.js
index 6b8e509c0..fccf6b35e 100644
--- a/tests/ffi/tests/test.js
+++ b/tests/ffi/tests/test.js
@@ -637,7 +637,7 @@ await dylib.symbols.call_fn_ptr_return_u8_thread_safe(returnU8Callback.pointer);
 
 // Test statics
 assertEquals(dylib.symbols.static_u32, 42);
-assertEquals(dylib.symbols.static_i64, -1242464576485);
+assertEquals(dylib.symbols.static_i64, -1242464576485n);
 assert(
   typeof dylib.symbols.static_ptr === "object"
 );