pump/* add a api to get binlog by ts

[july2993]

What problem does this PR solve?

add a api to get binlog by ts for debug
issue: https://internal.pingcap.net/jira/browse/TOOL-794

What is changed and how it works?

/debug/binlog/ to display the binlog info

Check List

Tests

• Manual test (add detailed scripts or steps below)
  query the api by some ts

tp:Commit start_ts:405815340898189313 commit_ts:405815340898189314 prewrite_key:"mDDLJobHi\377story\000\000\000\374\000\000\000\000\000\000\000H" ddl_query:"create table a(id int)" ddl_job_id:32

start_ts:405815381361688577 prewrite_key:"t\200\000\000\000\000\000\000\037_r\200\000\000\000\000\000\000\006" prewrite_value:"\010\020\022\014\010\037\022\006\010\014\010\002\010\0028\000"
 PrewriteValue:
schema_version:16 mutations:<table_id:31 inserted_rows:"\010\014\010\002\010\002" sequence:Insert >

[IANTHEREAL]

invalid parameter ts

[july2993]

@GregoryIan PTAL

[IANTHEREAL]

LGTM

[july2993]

@WangXiangUSTC PTAL

[WangXiangUSTC]

I think it's hard to know the commit ts when we debug, can we select by range?

[july2993]

I think it's hard to know the commit ts when we debug, can we select by range?

ts is a key point, we just want to dump the specified ts binlog.
but we can add a another api using the PullCommitBinlog for your use case, but don't change the PullComitBinlog api, you can just cancel the context when you get enough binlogs you want

[WangXiangUSTC]

I mean we may can't get the ts information when we debug, need get binlog by range.

[WangXiangUSTC]

LGTM