Replace lodash with eta

[rtritto]

lodash v4.18.0 introduced the issue lodash/lodash#6167 with lodash.template.

E.g.:

Error: Unable to generate service worker from template. 'assignWith is not defined'
    at populateSWTemplate (C:\Users\<USER>\AppData\Local\Yarn\Berry\cache\workbox-build-npm-7.4.0-c84561662c-10c0.zip\node_modules\workbox-build\build\lib\populate-sw-template.js:76:15)
    at writeSWUsingDefaultTemplate (C:\Users\<USER>\AppData\Local\Yarn\Berry\cache\workbox-build-npm-7.4.0-c84561662c-10c0.zip\node_modules\workbox-build\build\lib\write-sw-using-default-template.js:28:73)
    at generateSW (C:\Users\<USER>\AppData\Local\Yarn\Berry\cache\workbox-build-npm-7.4.0-c84561662c-10c0.zip\node_modules\workbox-build\build\generate-sw.js:95:23)

lodash.template is also deprecated (soruce lodash.template):

This package is deprecated. Use https://socket.dev/npm/package/eta instead.

lodash is used only in the workbox-build package (it uses lodash.template) and it can be replaced with eta (https://www.npmjs.com/package/eta).
The @types/lodash dependency at root package.json can be also be removed.

[google-cla]

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[rtritto]

@google-cla I signed the CLA