Adopt more eslint rules

[bajtos]

Rules to consider for enabling in @loopback/eslint-config:

• no-unsafe-call
• no-unsafe-member-access
• no-unsafe-return
• method-signature-style
• member-ordering (maybe not?)
• no-throw-literal - see feat(eslint-config): enable no-throw-literal rule #4404
• cyclomatic complexity
• max file size in lines
• prefer-readonly