Currently, we insert shim code into every piece of jitted code to handle the change in calling conventions from the interpreter and the jitted code.

We should, instead use a trampoline function. A trampoline function would perform the same job as the shim code,
but has many advantages:

1. we would only need one for the entire process, instead of one per executor.
2. we wouldn't need extra refcounting code to keep the shim alive as the trampoline function would always be live.
3. we can simplify the tier1 -> tier2 code in ENTER_EXECUTOR by having the trampoline manage much of the details
4. we can use the same interface for the tier 2 interpreter, further simplifying the code
5. we only need one entry into the JIT code. No need for jit_side_entry

Linked PRs

• GH-137959: Replace shim code in jitted code with a single trampoline function. #137961
• GH-137959: fix warning 'visibility' attribute ignored in jit/trampoline.c #140286
• gh-137959: Fix TIER1_TO_TIER2 macro name in JIT InternalDocs #141496