Turbopack: generate less JS before minification (#75358)
Use the final `__turbopack_context_.X` directly, which saves use the long destructuring.
The original versions (`__turbopack_load__`, `__turbopack_import__`) are still available as the user-facing API (implemented via free var replacements).
src-rolldown-1000 before:
```
input_len 6.776151mb
output_len 1.318701mb
```
src-rolldown-1000 after:
```
input_len 2.879056mb
output_len 1.147727mb
```
```
canary (0f7251fc78):
without sourcemaps:
15,3
506.01s user 104.05s system 780% cpu 1:18.21 total
500.73s user 105.54s system 767% cpu 1:18.98 total
with sourcemaps:
23,3gb
542.87s user 119.60s system 752% cpu 1:28.06 total
537.84s user 117.53s system 799% cpu 1:22.02 total
```
```
after (e09b2a5517):
without sourcemaps:
14,65gb
503.89s user 102.31s system 770% cpu 1:18.63 total
493.39s user 100.04s system 768% cpu 1:17.18 total
494.93s user 101.16s system 769% cpu 1:17.44 total
with sourcemaps:
22,7
529.38s user 115.85s system 785% cpu 1:22.09 total
522.39s user 115.70s system 781% cpu 1:21.66 total
```
