Switch prongs do not inherit runtime safety of parent block

[amp-59]

Zig Version

0.12.0-dev.1835+697b8f7d2

Steps to Reproduce and Observed Behavior

Compile example program with zig build-obj runtime_safety_switch_prong_error.zig runtime_safety_switch_prong_error.zig:

pub fn panic(_: []const u8, _: @TypeOf(@errorReturnTrace()), _: ?usize) noreturn {
    @compileError("");
}
pub export fn entry() usize {
    @setRuntimeSafety(false);
    var u: usize = 0;
    switch (u) {
        else => {
            // @setRuntimeSafety(false);
            u += 1;
        },
    }
    return u;
}

Result:

zig build-obj runtime_safety_switch_prong_error.zig
runtime_safety_switch_prong_error.zig:2:5: error:
    @compileError("");
    ^~~~~~~~~~~~~~~~~

Expected Behavior

Compile example program with zig build-obj runtime_safety_block_correct.zig runtime_safety_block_correct.zig:

pub fn panic(_: []const u8, _: @TypeOf(@errorReturnTrace()), _: ?usize) noreturn {
    @compileError("");
}
pub export fn entry() usize {
    @setRuntimeSafety(false);
    var u: usize = 0;
    {
        u += 1;
    }
    if (true) {
        u += 1;
    }
    while (true) {
        u += 1;
    }
    for (0..1) |_| {
        u += 1;
    }
    return u;
}

Result:

zig build-obj runtime_safety_block_correct.zig

Behaviour should be consistent with other sub-blocks.