[clang][ThreadSafety] Improve errors for trylock functions

[dmcardle]

Originally, I merged the half-baked #95290, but reverted it in #97293.

Based on feedback, I plan to make the following changes before relanding:

• Rather than locking down trylock function return types to a fixed set of types, require that they are contextually convertible to bool. This allows for smart pointers.
• Restrict success expressions to integer/bool literals.
  • Clarify in docs that it's not an equality comparison, but a conversion after conversion to bool.
  • Explicitly disallow enumerator success expressions? This avoids suggesting that anything other than a bool conversion is happening. More discussion here: [clang][ThreadSafety] Check trylock function success and return types #95290 (comment)
• Explicitly handle each allowed success expr type in getMutexIDs() rather than using EvaluateAsBooleanCondition().
• Potentially add a flag that disables any new errors/warnings to enable codebases to gradually fix their annotations.