ci: Enable LeakSanitizer in bindings-rust-asan

[axic]

Part of #614.

[axic]

Tested this with introducing a leak: https://app.circleci.com/pipelines/github/wasmx/fizzy/6898/workflows/fa937f8b-c3b3-4291-bbb3-2550ab9d2e94/jobs/62254

[codecov]

Codecov Report

Merging #820 (1ae9b34) into master (c341e3a) will decrease coverage by 0.00%.
The diff coverage is 100.00%.

❗ Current head 1ae9b34 differs from pull request most recent head a0df442. Consider uploading reports for the commit a0df442 to get more accurate results

@@            Coverage Diff             @@
##           master     #820      +/-   ##
==========================================
- Coverage   99.10%   99.10%   -0.01%     
==========================================
  Files          86       86              
  Lines       13017    13015       -2     
==========================================
- Hits        12900    12898       -2     
  Misses        117      117              

Flag	Coverage Δ
rust	99.60% <100.00%> (-0.01%)	⬇️
spectests	89.98% <ø> (ø)
unittests	98.94% <ø> (ø)
unittests-32	99.03% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
bindings/rust/src/lib.rs	99.89% <100.00%> (-0.01%)	⬇️

[axic]

As feared the leak sanitizer is on by default now: https://app.circleci.com/pipelines/github/wasmx/fizzy/6907/workflows/0618375e-8c94-495c-8477-8f7ed74f9521/jobs/62402

[axic]

It seems to be on-by-default, also suggested by https://clang.llvm.org/docs/LeakSanitizer.html.