feat(modelarmor): Added code samples for screening user prompt, model response and a PDF file

[tirthrajsinh-zala-crest]

Description

Created samples for user prompt and model response sanitation using model armor APIs.

Checklist

• I have followed Sample Format Guide
• pom.xml parent set to latest shared-configuration
• Appropriate changes to README are included in PR
• These samples need a new API enabled in testing projects to pass (let us know which ones)
• These samples need a new/updated env vars in testing projects set to pass (let us know which ones)
• Tests pass: mvn clean verify required
• Lint passes: mvn -P lint checkstyle:check required
• Static Analysis: mvn -P lint clean compile pmd:cpd-check spotbugs:check advisory only
• This sample adds a new sample directory, and I updated the CODEOWNERS file with the codeowners for this sample
• This sample adds a new Product API, and I updated the Blunderbuss issue/PR auto-assigner with the codeowners for this sample
• Please merge this PR for me once it is approved

[gemini-code-assist]

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[telpirion]

This PR has the same global issues as #10068 .

See internal discussion about content.

[harshnasitcrest]

This PR has the same global issues as #10068 .

See internal discussion about content.

@telpirion Thanks for your review! All global issues have been resolved in this PR along with sensitive content replaced based on GoogleCloudPlatform/python-docs-samples#13305

I will include additional tests, along with a sample of the Advanced SDP template, in a separate PR. This will prevent the increased diff from making it difficult for review.

[snippet-bot]

Here is the summary of changes.

You are about to add 3 region tags.

• modelarmor/src/main/java/modelarmor/SanitizeModelResponse.java:19, tag modelarmor_sanitize_model_response
• modelarmor/src/main/java/modelarmor/SanitizeUserPrompt.java:19, tag modelarmor_sanitize_user_prompt
• modelarmor/src/main/java/modelarmor/ScreenPdfFile.java:19, tag modelarmor_screen_pdf_file

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[harshnasitcrest]

@telpirion Merge conflicts are resolved on this branch. Tests and lints are passing locally. Could you proceed with merging this PR?