Currently wasm lazy tiering is enabled by default only for content that uses
the wasm-GC feature set. This patch enables lazy tiering for all wasm content.
Lazy tiering is disallowed if the "test serialization" pref is enabled, or if
no helper threads are available.
As a ridealong fix, a potential race in CanFlushExecutionContextForAllThreads
is fixed -- applies to 32- and 64-bit ARM on Linux and Android only.
There are also some fixes for jit-test tests:
* a new testing function, wasmLazyTieringEnabled, which indicates whether
compilation will be done using lazy tiering.
* wasm/binary-to-text.js, wasm/gc/speculative-inlining.js,
wasm/lazy-tiering-codegen.js: consistently use wasmLazyTieringEnabled
in the skip-if clauses, instead of ad-hoc other logic.
Differential Revision: https://phabricator.services.mozilla.com/D244195
