[roll] Roll fuchsia [dwc3][test] Harden test fixture teardown and early initialization

This addresses state isolation concerns by introducing strict teardown
routines in the test fixture to reset mock MMIO callbacks and explicitly
destroy the driver environment before exiting the test case.

This isolates the test environment and replaces the previous attempt to
zero-initialize DMA buffers, as the flakiness was root-caused to mock
state leakage between parallel test iterations rather than OS-level
memory recycling.

This also adds a safeguard to ~Dwc3 to avoid a panic if early driver
initialization fails before the BTI is fully established.

Original-Original-Bug: b/509735595
Test: fx test dwc3-test --count 500

Original-Original-Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/1650936
Original-Original-Revision: 03191f5b7b0df6f97e52512ca26ae1961dddd277
GitOrigin-RevId: 7f7931768f7194c5997de9442efef0058dfe68c8
Change-Id: I013b7077a81273d5772a00ea8273626cea0fd9e3
Reviewed-on: https://fuchsia-review.googlesource.com/c/integration/+/1682109
Cr-Commit-Position: refs/heads/main@{#195669}