[C++] uniform identifiers naming style.

[ffacs]

          Unrelated to this PR: we have many weird `_xxx` variable names appearing in the function signature. I'm thinking to do something like apache/arrow, which only use `xxx_` as the name of private class member variables. In this way, we can get rid of the weird case like this.

Originally posted by @wgtmac in #1761 (comment)

[ffacs]

The following .clang-tidy file can help us to check naming styles mismatch. And we can use clang-tidy to fix them.

Checks: "-*,
        readability-identifier-naming,
"

CheckOptions:
  [
      { key: readability-identifier-naming.PrivateMemberSuffix,   value: "_"  },
  ]

WarningsAsErrors: ''
HeaderFilterRegex: ''
FormatStyle:     none

But there is a problem that some protected/public variables need to be initialized on construction, what should the naming of
corresponding parameter should be? What do you think? @wgtmac @dongjoon-hyun

[wgtmac]

Could we add NOLINT to those public/protected variables?

[ffacs]

Could we add NOLINT to those public/protected variables?

Sorry for my confusing expression. What I mean just like below

orc/c++/src/ConvertColumnReader.cc

Lines 26 to 33 in e1f185e

	ConvertColumnReader::ConvertColumnReader(const Type& _readType, const Type& fileType,
	StripeStreams& stripe, bool _throwOnOverflow)
	: ColumnReader(_readType, stripe), readType(_readType), throwOnOverflow(_throwOnOverflow) {
	reader = buildReader(fileType, stripe, /*useTightNumericVector=*/true,
	/*throwOnOverflow=*/false, /*convertToReadType*/ false);
	data =
	fileType.createRowBatch(0, memoryPool, /*encoded=*/false, /*useTightNumericVector=*/true);
	}

The readType is a protected member of ConvertColumnReader. if we still use readType as the name, we can`t uniform the naming of constructor parameter.

[wgtmac]

What about this?

• Use _ suffix for private member variable.
• Do not use _ suffix for protected and public member variable.
• Avoid any _ prefix and suffix in any function parameter.

[dongjoon-hyun]

Can we borrow some existing styles from other open source projects?
IIRC, initially, @wgtmac mentioned Arrow community. Are the above rules came from Arrow community?

[dongjoon-hyun]

For the record, I welcome any linter-based rules. Thank you for making this efforts, @ffacs and @wgtmac .

[wgtmac]

We could leverage https://clang.llvm.org/extra/clang-tidy/checks/readability/identifier-naming.html for variable naming. Apache Arrow used cpplint approach which we cannot borrow: https://github.com/apache/arrow/blob/main/cpp/build-support/cpplint.py