[PATCH] bootstrap: tweak verbosity settings

[PATCH] bootstrap: tweak verbosity settings

Currently the verbosity settings are:
- 2: RUSTC-SHIM envvars get spammed on every invocation, O(30) lines
     cargo is passed -v which outputs CLI invocations, O(5) lines
- 3: cargo is passed -vv which outputs build script output, O(0-10) lines

This commit changes it to:

- 1: cargo is passed -v, O(5) lines
- 2: cargo is passed -vv, O(10) lines
- 3: RUSTC-SHIM envvars get spammed, O(30) lines

Gbp-Pq: Name u-89950.patch