chore(jobs): add normalized region tags with product prefix

[meredithslota]

Adds "dual-homed" region tags with product prefix to enable better sample tracking. Will send a CL to update relevant docs and then remove the obsolete region tags in a separate PR.

[snippet-bot]

Here is the summary of changes.

You are about to add 7 region tags.

• jobs/v3/src/main/java/com/google/samples/GeneralSearchSample.java:61, tag job_discovery_basic_keyword_search
• jobs/v3/src/main/java/com/google/samples/GeneralSearchSample.java:101, tag job_discovery_category_filter_search
• jobs/v3/src/main/java/com/google/samples/GeneralSearchSample.java:141, tag job_discovery_employment_types_filter_search
• jobs/v3/src/main/java/com/google/samples/GeneralSearchSample.java:181, tag job_discovery_date_range_filter_search
• jobs/v3/src/main/java/com/google/samples/GeneralSearchSample.java:230, tag job_discovery_language_code_filter_search
• jobs/v3/src/main/java/com/google/samples/GeneralSearchSample.java:270, tag job_discovery_company_display_name_search
• jobs/v3/src/main/java/com/google/samples/GeneralSearchSample.java:310, tag job_discovery_compensation_search

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