[logger] eliminate expensive regex

[xirzec]

This was flagged by an automated tool as a bad code pattern:

azure-sdk-for-js/sdk/core/logger/src/debug.ts

Line 100 in 6b40ae5

skippedNamespaces.push(new RegExp(`^${ns.substr(1)}$`));

and

azure-sdk-for-js/sdk/core/logger/src/debug.ts

Line 102 in 6b40ae5

enabledNamespaces.push(new RegExp(`^${ns}$`));

Perhaps we can clean this code up or consider taking a dependency on debug directly now that we aren't trying to support IE11...

[github-actions]

@deyaaeldeen @jeremymeng @joheredi @maorleger @mpodwysocki @timovv @xirzec

[github-actions]

Thank you for your feedback. Tagging and routing to the team member best able to assist.