Potential high loads against TXE in noir-projects+test-contracts with multi-threading

[jeanmon]

In a recent PR, I experienced several times failure on ./noir-projects+test-contracts
By running the "full test" locally on mainframe (in noir-projects/noir-contracts):
NARGO_FOREIGN_CALL_TIMEOUT=300000 ../../noir/noir-repo/target/release/nargo test --silence-warnings --oracle-resolver http://localhost:8080/
I got similar failures again. Alvaro helped me and found out that by running the tests separately such as:

NARGO_FOREIGN_CALL_TIMEOUT=300000 ../../noir/noir-repo/target/release/nargo test --silence-warnings --oracle-resolver http://localhost:8080/ --package token_contract burn_private

or by limiting the number of thread to 1 --test-threads=1,
these tests were passing. After multiple reruns it became green on CI.
What Alvaro is suspecting is too much load to the TXE which might lead to some flake failures. Possibly, limiting this test with less threads might be a solution.