[DOCS-10684] PR Gates renaming

[joepeeples]

What does this PR do? What is the motivation?

Renames Quality Gates to PR Gates.

Merge instructions

Important

🚧 WORK IN PROGRESS 🚧 Not ready for review yet.

Merge readiness:

• Ready for merge

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Additional notes

[github-actions]

Preview links (active after the build_preview check completes)

New or renamed files

• https://docs-staging.datadoghq.com/joepeeples/10684-pr-gates/pr_gates/
• https://docs-staging.datadoghq.com/joepeeples/10684-pr-gates/pr_gates/explorer/
• https://docs-staging.datadoghq.com/joepeeples/10684-pr-gates/pr_gates/guide/
• https://docs-staging.datadoghq.com/joepeeples/10684-pr-gates/pr_gates/search/

Removed or renamed files (these should redirect)

• https://docs-staging.datadoghq.com/joepeeples/10684-pr-gates/quality_gates/
• https://docs-staging.datadoghq.com/joepeeples/10684-pr-gates/quality_gates/explorer/
• https://docs-staging.datadoghq.com/joepeeples/10684-pr-gates/quality_gates/guide/
• https://docs-staging.datadoghq.com/joepeeples/10684-pr-gates/quality_gates/search/

Renamed files

• https://docs-staging.datadoghq.com/joepeeples/10684-pr-gates/pr_gates/explorer/facets
• https://docs-staging.datadoghq.com/joepeeples/10684-pr-gates/pr_gates/explorer/saved_views/
• https://docs-staging.datadoghq.com/joepeeples/10684-pr-gates/pr_gates/explorer/search_syntax
• https://docs-staging.datadoghq.com/joepeeples/10684-pr-gates/pr_gates/guide/understanding_rule_scopes
• https://docs-staging.datadoghq.com/joepeeples/10684-pr-gates/pr_gates/setup/

Modified Files

• https://docs-staging.datadoghq.com/joepeeples/10684-pr-gates/account_management/audit_trail/events
• https://docs-staging.datadoghq.com/joepeeples/10684-pr-gates/data_security/data_retention_periods
• https://docs-staging.datadoghq.com/joepeeples/10684-pr-gates/getting_started/
• https://docs-staging.datadoghq.com/joepeeples/10684-pr-gates/getting_started/code_security/
• https://docs-staging.datadoghq.com/joepeeples/10684-pr-gates/tests/flaky_test_management/early_flake_detection