fix(role): preserve SCRAM password verifiers

[damacus]

Summary

• preserve pre-computed SCRAM-SHA-256 verifiers verbatim through the Ruby pg connection
• quote plaintext and encrypted password values with libpq's connection-aware literal escaping
• prevent password-bearing SQL and query results from being written to debug logs
• document creation and rotation semantics for encrypted role passwords
• remove the obsolete ChefSpec Berkshelf plugin required by the v9 lint workflow

Testing

• cookstyle .
• yamllint .
• markdownlint-cli2 '**/*.md'
• RSpec: 67 examples, 0 failures
• access-15-ubuntu-2404: 36 successful, 0 failures
• access-16-ubuntu-2404: 36 successful, 0 failures
• access-17-ubuntu-2404: 36 successful, 0 failures
• access-17-almalinux-9: 36 successful, 0 failures

Closes #703.
Replaces #797, whose shell-specific dollar-sign escaping is no longer valid after the cookbook moved SQL execution to PG::Connection.

[github-actions]

Slowest examples

Top 10 slowest examples (0.01 seconds, 37.93% of total time)

Example	Description	Time in seconds
spec/libraries/helpers_spec.rb:19	PostgreSQL::Cookbook::Helpers#data_dir(version) with rhel family and Postgres 11 from repo returns the correct path	0.00635
spec/libraries/helpers_spec.rb:132	PostgreSQL::Cookbook::Helpers#dnf_module_platform? returns false on RHEL 7	0.00114
spec/libraries/helpers_spec.rb:81	PostgreSQL::Cookbook::Helpers#conf_dir(version) with debian family and Postgres 11 from os returns the correct path	0.00054
spec/libraries/role_spec.rb:18	PostgreSQL::Cookbook::SqlHelpers::Role#role_password_sql quotes a SCRAM-SHA-256 verifier without modifying dollar signs	0.0005
spec/libraries/helpers_spec.rb:65	PostgreSQL::Cookbook::Helpers#conf_dir(version) with rhel family and Postgres 13 from os returns the correct path	0.00048
spec/libraries/helpers_spec.rb:43	PostgreSQL::Cookbook::Helpers#data_dir(version) with debian family and Postgres 11 from os returns the correct path	0.00047
spec/libraries/helpers_spec.rb:119	PostgreSQL::Cookbook::Helpers#default_platform_service_name(version) with debian family and Postgres 11 from os returns the correct service name	0.00046
spec/libraries/helpers_spec.rb:95	PostgreSQL::Cookbook::Helpers#default_platform_service_name(version) with rhel family and Postgres 12 from repo returns the correct service name	0.00042
spec/libraries/role_spec.rb:27	PostgreSQL::Cookbook::SqlHelpers::Role#role_password_sql uses connection-aware quoting for a plaintext password	0.00042
spec/libraries/helpers_spec.rb:150	PostgreSQL::Cookbook::Helpers#dnf_module_platform? returns false on RHEL 10	0.00041