command: extend `select` api support

[denizsurmeli]

This PR extends the support for AWS S3's Select API.

Resolves #494, resolves #357 .

[denizsurmeli]

The aws-sdk-go version that we use have a bug that it logs the response header regardless of the log level set in s5cmd. Here is the related issue, so I will bump to the version that has the fix and check if anything breaks.

[denizsurmeli]

Minio panics during SELECT queries. Open to suggestions about testing.

panic: runtime error: index out of range [0] with length 0

goroutine 779 [running]:
github.com/minio/minio/internal/s3select/csv.NewReader.func1({0x5929480?, 0xc0093743f0?})
    github.com/minio/minio/internal/s3select/csv/reader.go:306 +0x425
github.com/minio/minio/internal/s3select/csv.(*Reader).startReaders.func3()
    github.com/minio/minio/internal/s3select/csv/reader.go:244 +0x19c
created by github.com/minio/minio/internal/s3select/csv.(*Reader).startReaders
    github.com/minio/minio/internal/s3select/csv/reader.go:233 +0x705

[denizsurmeli]

Minio panics during SELECT queries. Open to suggestions about testing.

panic: runtime error: index out of range [0] with length 0

goroutine 779 [running]:
github.com/minio/minio/internal/s3select/csv.NewReader.func1({0x5929480?, 0xc0093743f0?})
  github.com/minio/minio/internal/s3select/csv/reader.go:306 +0x425
github.com/minio/minio/internal/s3select/csv.(*Reader).startReaders.func3()
  github.com/minio/minio/internal/s3select/csv/reader.go:244 +0x19c
created by github.com/minio/minio/internal/s3select/csv.(*Reader).startReaders
  github.com/minio/minio/internal/s3select/csv/reader.go:233 +0x705

Minio panics only on CSV queries that you don't specify the delimiter, which is weird that it does not validate the delimiter in the request, JSON queries seemed fine.

[igungor]

PR also fixes #357 @denizsurmeli

[denizsurmeli]

Refactored/fixed the comments.

[igungor]

I'd like to share my expectations while playing with this feature:

1. Expected CSV output if I query CSV objects (same thing for TSV, or other formats).

./s5cmd select csv --delimiter "," -e 'select * from s3object' 's3://bucket/ibrahim/s5cmd-select/prices.csv'
{"_1":"id","_2":"name","_3":"price"}
{"_1":"1","_2":"avocado","_3":"3.99"}
{"_1":"2","_2":"banana","_3":"1.99"}
{"_1":"3","_2":"cabbage","_3":"0.99"}

2. How do I query TSV files?

   ./s5cmd select csv --output-format csv --delimiter "\t" -e 'select * from s3object' 's3://bucket/ibrahim/s5cmd-select/prices.tsv'
   ERROR "select csv --delimiter=\\t --query=select * from s3object --output-format=csv s3://bucket/ibrahim/s5cmd-select/prices.tsv": InvalidRequestParameter: The value of parameter FieldDelimiter is invalid. Please check the service documentation and try again. status code: 400, request id: ...

[denizsurmeli]

I'd like to share my expectations while playing with this feature:

1. Expected CSV output if I query CSV objects (same thing for TSV, or other formats).

./s5cmd select csv --delimiter "," -e 'select * from s3object' 's3://bucket/ibrahim/s5cmd-select/prices.csv'
{"_1":"id","_2":"name","_3":"price"}
{"_1":"1","_2":"avocado","_3":"3.99"}
{"_1":"2","_2":"banana","_3":"1.99"}
{"_1":"3","_2":"cabbage","_3":"0.99"}

2. How do I query TSV files?

./s5cmd select csv --output-format csv --delimiter "\t" -e 'select * from s3object' 's3://bucket/ibrahim/s5cmd-select/prices.tsv'
ERROR "select csv --delimiter=\\t --query=select * from s3object --output-format=csv s3://bucket/ibrahim/s5cmd-select/prices.tsv": InvalidRequestParameter: The value of parameter FieldDelimiter is invalid. Please check the service documentation and try again. status code: 400, request id: ...

For the first issue, you are right, I have implemented the feature. For the second question, I have added an example query to the help command. I have also extended the flag descriptions.

[denizsurmeli]

Applied the suggestions and refactored the code. @igungor