Batch load regions when building tikv coprocessor tasks

[you06]

Enhancement

#51326 implements batch loading region cache for tiflash coprorcessor, this can also be used by tikv if we support batch load.

Further, there can be some optimizations:

1. Support scan non-continuous region scanning.
2. If there are some region cache hit in the given range, we can skip them.

[you06]

Result of test limit 1 case:

1. split table into 1000 regions by SPLIT TABLE sbtest1 BETWEEN (0) AND (1000000) REGIONS 1000;
2. wait until region cache expired.
3. run a simple query explain analyze select * from sbtest1 limit 1;

• Without this interface: ...build_task_duration: 81.5ms..., statmenet execution takes 0.11 sec
• With this interface: ...build_task_duration: 2.7ms..., statement execution takes 0.02 sec