expression: implement vectorized evaluation for builtinCastDurationAsRealSig

[pingyu]

PCP #12105

What problem does this PR solve?

Implement vectorized evaluation for builtinCastDurationAsRealSig at #12105

What is changed and how it works?

It gets faster about 1.2%.
Duration.ToNumber() is modified, just as what is done in CheckFsp() from fsp.go. Otherwise builtinCastDurationAsRealSig.evalReal() in builtin_cast.go will raise a runtime error: slice bounds out of range [:-1] in unittest of builtinCastDurationAsRealSig.vecEvalReal().

Check List

Tests

• Unit test

> GO111MODULE=on go test -check.f TestVectorizedBuiltinCastFunc
PASS: builtin_cast_vec_test.go:130: testEvaluatorSuite.TestVectorizedBuiltinCastFunc	0.134s
OK: 1 passed
PASS
ok  	github.com/pingcap/tidb/expression	0.158s

• Benchmark

> go test -v -benchmem -bench=BenchmarkVectorizedBuiltinCastFunc -run=BenchmarkVectorizedBuiltinCastFunc -args builtinCastDurationAsRealSig
goos: darwin
goarch: amd64
pkg: github.com/pingcap/tidb/expression
BenchmarkVectorizedBuiltinCastFunc/builtinCastDurationAsRealSig-VecBuiltinFunc-12         	    4402	    255587 ns/op	   50713 B/op	    3669 allocs/op
BenchmarkVectorizedBuiltinCastFunc/builtinCastDurationAsRealSig-NonVecBuiltinFunc-12      	    4347	    277312 ns/op	   50712 B/op	    3669 allocs/op
PASS
ok  	github.com/pingcap/tidb/expression	2.430s

[sre-bot]

Thanks for your contribution. If your PR get merged, you will be rewarded 50 points.

[wshwsh12]

LGTM

[codecov]

Codecov Report

Merging #13475 into master will increase coverage by 0.0462%.
The diff coverage is 61.5384%.

@@               Coverage Diff                @@
##             master     #13475        +/-   ##
================================================
+ Coverage   80.2004%   80.2467%   +0.0463%     
================================================
  Files           472        472                
  Lines        114866     114791        -75     
================================================
- Hits          92123      92116         -7     
+ Misses        15495      15449        -46     
+ Partials       7248       7226        -22

[qw4990]

/run-all-tests

[qw4990]

/rebuild

[qw4990]

LGTM

[sre-bot]

@pingyu complete task #12105 and get 50 score, currerent score 250.