fix: mark database drivers as optional peer dependencies

[DRoet]

Pull Request check-list

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Description of change

When using yarn 2 and PnP, it will throw an error because sequelize is trying to access the database drivers without listing them as direct dependencies/peerDependencies in package.json

(node:13140) [MODULE_NOT_FOUND] Error: sequelize tried to access mysql2, but it isn't declared in its dependencies; this makes the require call ambiguous and unsound.

Since we don't want to list them as direct dependencies, we can fix this error by listing all the database drivers as optional peer dependencies using the new peerDependenciesMeta field.

[codecov]

Codecov Report

Merging #12484 into v6 will increase coverage by 0.49%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##               v6   #12484      +/-   ##
==========================================
+ Coverage   95.95%   96.45%   +0.49%     
==========================================
  Files          92       95       +3     
  Lines        8951     9155     +204     
==========================================
+ Hits         8589     8830     +241     
+ Misses        362      325      -37     

Impacted Files	Coverage Δ
lib/dialects/mariadb/connection-manager.js	100.00% <0.00%> (ø)
lib/dialects/mariadb/index.js	100.00% <0.00%> (ø)
lib/dialects/mariadb/query.js	87.96% <0.00%> (ø)
lib/sequelize.js	95.87% <0.00%> (+0.63%)	⬆️
lib/dialects/postgres/connection-manager.js	95.80% <0.00%> (+1.39%)	⬆️
lib/dialects/abstract/query-interface.js	94.08% <0.00%> (+1.86%)	⬆️
lib/dialects/mariadb/data-types.js	100.00% <0.00%> (+52.63%)	⬆️
lib/dialects/mariadb/query-generator.js	100.00% <0.00%> (+81.25%)	⬆️

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[sushantdhiman]

LGTM, needs a PR to master first

[DRoet]

@sushantdhiman see #12494

[sushantdhiman]

🎉 This PR is included in version 6.3.3 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

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