fix and optimize openjpeg J2C encoder

[chanayane]

This is a follow up of my previous PR about JPEG2000 encoding with OpenJPEG. #2054

There were a few issues with my previous attempt:

• parameters.tcp_rates were either wrong or ignored due to the use of max_cs_size, so possibly there were some layers that were over compressed or simply non existant
• Use of some magical numbers (the 2, 4 and 15 multipliers) to compute rates. I used those numbers to try getting file sizes similar to the ones I got with Kakadu, but I decided to proceed differently with a clearer approach

Here's what I did in this PR:

• Added a function that returns a number of layers, between 2 to 6, depending on the image surface
• Added a function that compute and fills parameters.tcp_rates using a geometrical sequence. The file size will now respect the ideal goal of 1:8 compression ratio. Each subsequent layer will have a rate that is 4 times the previous rate.
• Stopped using max_cs_size. It's not needed if tcp_rates are set correctly
• Reworked the opj_read, opj_write, opj_seek, opj_skip, opj_free_user_data and opj_free_user_data_write functions with more optimized and safe equivalents
• Simplified setImage function

After a lot of testing I came very close to the results we get
with Kakadu. Here are some test files for comparison:
test_files.zip

The encoded files now respect the 1:8 ratio and have the correct number of discards.

With many thanks to @TommyTheTerrible for his help.

[marchcat]

Thank you for your contribution!

Please fix the whitespace issues so that it passes the pre-commit check.

[marchcat]

Suggested change

	llassert(user_data);
	llassert(user_data);

[marchcat]

Suggested change

	parameters->tcp_numlayers = num_layers;
	parameters->tcp_numlayers = num_layers;

[marchcat]

Suggested change

	parameters.tcp_mct = (image->numcomps >= 3) ? 1 : 0; // no color transform for RGBA images
	parameters.tcp_mct = (image->numcomps >= 3) ? 1 : 0; // no color transform for RGBA images