Update LoopBack 3 status to end-of-life (EOL)

[achrinza]

This issue is to keep a consolidated list of pull requests to update the LoopBack 3 status from Maintenance LTS to End-of-Life (EOL).

• eslint-config-loopback
• generator-loopback (chore: update LTS status to End-of-Life strongloop/generator-loopback#420)
• gulp-loopback-sdk-angular (chore: update LTS status to End-of-Life strongloop/gulp-loopback-sdk-angular#24)
• grunt-loopback-sdk-angular (chore: update LTS status to End-of-Life strongloop/grunt-loopback-sdk-angular#40)
• icars-server
• loopback-next (chore: update LB3 LTS status to EOL #6908) (TODO: Put up notice about EOL of LB3 on relevant pages and packages #6969)
• loopback (chore: update LTS status to End-of-Life strongloop/loopback#4343)
• loopback-api-definition
• loopback-boot (chore: update LTS status to End-of-Life strongloop/loopback-boot#308)
• loopback-cli (chore: update LTS status to End-of-Life strongloop/loopback-cli#102)
• loopback-component-oauth2
• loopback-component-explorer
• loopback-component-passport
• loopback-component-push
• loopback-connector-remote (docs: end of life strongloop/loopback-connector-remote#106)
• loopback-context (chore: update LTS status to End-of-Life strongloop/loopback-context#56)
• loopback-datasource-juggler(chore: update 3.x LTS to End-of-Life loopback-datasource-juggler#1888)
• loopback-example-facade
• loopback-filters (chore: update LTS status to End-of-Life strongloop/loopback-filters#37)
• loopback-getting-started
• loopback-getting-started-intermediate
• loopback-multitenancy
• loopback-multitenant-poc
• loopback-phase
• loopback-sdk-angular-cli
• loopback-soap
• loopback-swagger
• loopback-utils
• loopback-workspace
• loopback.io (feat: update LB3 LTS status loopback.io#1125, fix: LoopBack 3 LTS status on homepage loopback.io#1156)
• poc-loopback-multitenancy
• strong-remoting

Put a notice about LB3's EOL on the following pages.

• https://github.com/strongloop/loopback-next/tree/master/packages/booter-lb3app
• https://github.com/strongloop/loopback-next/tree/master/examples/lb3-application
• https://loopback.io/doc/en/lb4/migration-overview.html
• https://loopback.io/doc/en/lb4/migration-mounting-lb3app.html
• https://loopback.io/doc/en/lb3/index.html