Use saturating counters for branch taken counters in `_POP_JUMP_IF_FALSE` and similar instructions.

Each conditional branch instruction contains a 16 bit field for recording the direction of the last 16 jumps.

    uint16_t *branches;

    uint16_t val = *branches;
    val = (val << 1) | direction;
    *branches =val;

This tells the direction of the last 16 branches.
When recording traces for the JIT, 16 branches is not a lot of information to guide region selection.

Instead, we could record the count of the two directions instead using a pair of saturating 8 bit counters.

    uint8_t branches[2];

    branches[direction] += (branches[direction] != 255);

Which is only one extra ALU instruction for most C compilers, and no extra memory accesses.

With a JIT warmup of up 500, we can get precise numbers of the branches taken.
With a warmup of a 1000, the saturating counters can still distinguish between branches that are rarely taken and those which are more balanced.

For example, if a branch switches direction every 20 times, the current counter might show a perfectly biased branch, but the saturating counter approach will show that the branch is roughly balanced.

从 _POP_JUMP_IF_FALSE 指令和类似的条件分支实现开始，然后追踪它们的分支数据是如何为 JIT 跟踪记录的。当方向计数使用两个饱和计数器、上限为 255，并在不改变指令行为的情况下提供所提议的预热信息时，这项更改就完成了。