Merge bitcoin/bitcoin#35773: test: Suppress implicit-unsigned-integer-truncation:SaltedCoinsCacheHasher::operator()

fa7f553781 test: Suppress implicit-unsigned-integer-truncation:SaltedCoinsCacheHasher::operator() (MarcoFalke)

Pull request description:

  The truncation of u64 to size_t is intentional here, but it would be nice to document that for ubsan.

  Otherwise, ubsan will print warnings about this. E.g. on 32-bit platforms:

  ```
  /ci_container_base/src/coins.h:255:16: runtime error: implicit conversion from type 'uint64_t' (aka 'unsigned long long') of value 18400304222395891501 (64-bit, unsigned) to type 'size_t' (aka 'unsigned int') changed the value to 2265382701 (32-bit, unsigned)
  ```

  This is a bit tedious to test on 64-bit platforms, but one can use a diff like:

  ```diff
  diff --git a/src/coins.h b/src/coins.h
  index c854893bcb..906be9efae 100644
  --- a/src/coins.h
  +++ b/src/coins.h
  @@ -246,3 +246,3 @@ public:
       /** Hash a transaction ID, itself a cryptographic hash, as one jumbo block. */
  -    size_t operator()(const Txid& id) const noexcept
  +    uint32_t operator()(const Txid& id) const noexcept
       {
  @@ -252,3 +252,3 @@ public:
       /** Hash an outpoint as its txid jumbo block followed by the zero-extended index as one normal block. */
  -    size_t operator()(const COutPoint& id) const noexcept
  +    uint32_t operator()(const COutPoint& id) const noexcept
       {
  ```

  and:

  ```
  $ UBSAN_OPTIONS="suppressions=$(pwd)/test/sanitizer_suppressions/ubsan:print_stacktrace=1:halt_on_error=1:report_error_type=1" ./bld-cmake/bin/test_bitcoin

  ./src/coins.h:255:16: runtime error: implicit conversion from type 'uint64_t' (aka 'unsigned long') of value 17092028281225243117 (64-bit, unsigned) to type 'uint32_t' (aka 'unsigned int') changed the value to 291269101 (32-bit, unsigned)

ACKs for top commit:
  l0rinc:
    ACK fa7f553781
  sedited:
    ACK fa7f553781

Tree-SHA512: 0798e09a1291c7e7e2799c586f416b9e92ddf3ad64af3888a01726f338935f735c4e36716a7c38426e75ddbbdc2854949c3f553ab67758a053a2e3ba6a3c3ec1

test/sanitizer_suppressions/ubsan

@@ -61,6 +61,7 @@ implicit-integer-sign-change:crypto/
 implicit-integer-sign-change:TxConfirmStats::removeTx
 implicit-integer-sign-change:EvalScript
 implicit-signed-integer-truncation:crypto/
+implicit-unsigned-integer-truncation:SaltedCoinsCacheHasher::operator()
 implicit-unsigned-integer-truncation:crypto/
 shift-base:arith_uint256.cpp
 shift-base:crypto/