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.

從 _POP_JUMP_IF_FALSE 指令和類似的條件分支實作開始，接著追蹤它們的分支資料如何為 JIT 追蹤記錄。當方向計數使用兩個飽和計數器、上限為 255，並在不改變指令行為的情況下提供所提議的預熱資訊時，這項變更就完成了。