Fix Windows Path issue when using Background Image

[jakejackson1]

Description

Resolves an escaping issue with a windows-based path when using esc_url_raw() by conditionally using esc_attr() instead.

Testing instructions

1. Setup a PDF on a form and configure a Background Image
2. Verify the image displays in the PDF

Screenshots

Checklist:

• [ ] I've tested the code.
• [ ] My code is easy to read, follow, and understand
• [ ] My code follows the accessibility standards.
• [ ] My code has proper inline documentation / docblocks.

Additional Comments

[codecov[bot]]

Codecov Report

Merging #1402 (4585bb5) into development (a3291b5) will decrease coverage by 0.01%. The diff coverage is 100.00%.

@@                Coverage Diff                @@
##             development    #1402      +/-   ##
=================================================
- Coverage          77.28%   77.26%   -0.02%     
  Complexity          2898     2898              
=================================================
  Files                243      243              
  Lines              10103    10101       -2     
  Branches             370      370              
=================================================
- Hits                7808     7805       -3     
- Misses              2287     2288       +1     
  Partials               8        8              

Impacted Files	Coverage Δ
src/View/html/PDF/core_template_styles.php	98.00% <100.00%> (-0.08%)	:arrow_down:
src/Helper/Helper_Misc.php	76.36% <0.00%> (-0.37%)	:arrow_down:

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.

[jakejackson1]

@jestonihpi this PR needs to be checked to ensure the background image feature works correctly on a linux-based environment and a windows based environment please.

[jestonihpi]

@jakejackson1 copy.