Added check_open for PNG, JPEG, and EXR readers

[DharshanV]

Description

This PR is ment to address this feature request: https://github.com/AcademySoftwareFoundation/OpenImageIO/issues/3974

I added check_open for these file format's ImageInput while following each file specfication:

• PNG: https://www.w3.org/TR/png/#11IHDR
• JPEG: https://en.wikipedia.org/wiki/JPEG_File_Interchange_Format#JFIF_APP0_marker_segment
• EXR: https://openexr.com/en/latest/OpenEXRFileLayout.html#header-attributes-all-files

Tests

Checklist:

• [x] I have read the contribution guidelines.
• [ ] I have updated the documentation, if applicable. (Check if there is no need to update the documentation, for example if this is a bug fix that doesn't change the API.)
• [ ] I have ensured that the change is tested somewhere in the testsuite (adding new test cases if necessary).
• [ ] If I added or modified a C++ API call, I have also amended the corresponding Python bindings (and if altering ImageBufAlgo functions, also exposed the new functionality as oiiotool options).
• [x] My code follows the prevailing code style of this project. If I haven't already run clang-format before submitting, I definitely will look at the CI test that runs clang-format and fix anything that it highlights as being nonconforming.

[linux-foundation-easycla[bot]]

The committers listed above are authorized under a signed CLA.

• :white_check_mark: login: DharshanV / name: Dharshan Vishwanatha (6819d64e33f3e5beb27463eb65eeca0dcd3fcb9b, 0679c2cecb76cd0ebf672f74ebeaa9f3c439eab8)