wasm: make integer/string builtins available to the -os browser target

`int.str()` (and the other int→string helpers), the `min_int`/`max_int` builtin
constants, and `tos()` live in `int_notd_no_imports.v` /
`string_notd_no_imports.v`, which were only compiled for `-os wasi`. So on
`-os browser`, `println(int)`, `'${int}'` interpolation, integer concatenation,
and `min_int`/`max_int` all failed (checker: "does not have a .str() function" /
"undefined ident: max_int"; or at the encoder, "called function int.str does
not exist").

These helpers are pure (no imports, no wasi/JS-specific calls), so move them
from `vlib/builtin/wasm/wasi/` to the shared `vlib/builtin/wasm/` dir; both
browser and wasi builds pick them up. No symbol conflicts — neither the browser
nor the wasi builtin defines `tos` or `int.str`. Follow-up to #27450 (which
fixed the browser `eprintln` panic).

Adds vlib/v/gen/wasm/tests/browser_int_builtins_test.v.

Author: enghitalo

…/builtin/wasm/wasi/int_notd_no_imports.v vlib/builtin/wasm/int_notd_no_imports.vvlib/builtin/wasm/wasi/int_notd_no_imports.v renamed to vlib/builtin/wasm/int_notd_no_imports.v vlib/builtin/wasm/wasi/int_notd_no_imports.v renamed to vlib/builtin/wasm/int_notd_no_imports.v

@@ -0,0 +1,34 @@
+import os
+
+// On the `-os browser` target, integer-to-string (`int.str()`), `println(int)`,
+// string interpolation/concat of integers, and the `min_int`/`max_int` builtin
+// constants used to fail — their implementations live in
+// `vlib/builtin/wasm/int_notd_no_imports.v` / `string_notd_no_imports.v`, which
+// were only compiled for `-os wasi`. They are now in the shared
+// `vlib/builtin/wasm/` dir, so browser builds pick them up too.
+fn test_wasm_browser_target_can_format_integers() {
+	vexe := os.quoted_path(@VEXE)
+	wrkdir := os.join_path(os.vtmp_dir(), 'wasm_browser_int_tests')
+	os.mkdir_all(wrkdir)!
+	defer {
+		os.rmdir_all(wrkdir) or {}
+	}
+
+	source_path := os.join_path(wrkdir, 'ints.v')
+	output_path := os.join_path(wrkdir, 'ints.wasm')
+	source := [
+		'pub fn main() {',
+		'\tprintln(42)', // println(int) needs int.str()
+		'\tn := 7',
+		"\tprintln('value=' + n.str())", // explicit int.str() + string concat
+		'\t_ = max_int', // min_int/max_int builtin consts
+		'\t_ = min_int',
+		'}',
+	].join_lines()
+	os.write_file(source_path, source)!
+
+	res :=
+		os.execute('${vexe} -b wasm -os browser -o ${os.quoted_path(output_path)} ${os.quoted_path(source_path)}')
+	assert res.exit_code == 0, 'browser integer formatting failed to compile: ${res.output}'
+	assert os.exists(output_path), 'missing browser wasm output'
+}