Fix TextFormatMapTest.DynamicMessage issue#5136

[akjain2052]

Clean up a multi-line string to conform to Unix line endings.

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[akjain2052]

This is the fix for this Issue# #5136

Issue: Google_protobuf failed to run the TextFormatMapTest.DynamicMessage with release configuration and debug configuration #5136

Issue observed in: Windows OS

Reason for Issue: In windows OS, Each line ends with "CRLF" in a file. But in linux, Lines ends with "LF". In the TextFormatMapTest.DynamicMessage test case, Reading file in string contains "CRLF" at the end of each line which was the reason for string comparison failure. It was expecting "LF" instead of "CRLF".

Solution:
CleanStringLineEndings() is a method which cleans up a multi-line string to conform to Unix line endings.
This function call i.e. CleanStringLineEndings() was missing in "TextFormatMapTest.DynamicMessage" testcase.
A Similar change was added in "TextFormatMapTest.Sorted" test case where they were reading a file from windows OS, and making it compatible with linux using CleanStringLineEndings().

[akjain2052]

@googlebot I signed it!

[akjain2052]

Please help to review, and merge.

[acozzette]

Thanks, @akjain2052.