fix: resilient _VUE_DEVTOOLS_TOAST_

[timozander]

What kind of change does this PR introduce? (check at least one)

• Bugfix
• Feature
• Code style update
• Refactor
• Build-related changes
• Other, please describe:

Does this PR introduce a breaking change? (check one)

• Yes
• No

The PR fulfills these requirements:

• When resolving a specific issue, it's referenced in the PR's title (e.g. fix #xxx[,#xxx], where "xxx" is the issue number)
• All tests are passing
• New/updated tests are included

Other information:
When using Pinia v2 with the latest beta of Vue devtools, I always experience the following console error:

backend.js:3166 ReferenceError: __VUE_DEVTOOLS_TOAST__ is not defined
    at pinia.esm-bundler.js?v=94b0b286:232
    at Object.addPlugin (backend.js:3162)
    at Object.<anonymous> (backend.js:908)
    at Object.emit (<anonymous>:1:780)
    at Object._replayBuffer (<anonymous>:1:332)
    at Object.on (<anonymous>:1:424)
    at connect (backend.js:907)

While I cannot exactly pin down the exact cause of this, I think its reasonable to fall back to console output whenever the devtools's toast is not available

[posva]

This is weird since the devtools should be installed at that point. I would need to have more details to ensure this is the right fix

[timozander]

I found out that it is caused by the devtools failing to load a specific source (vuejs/devtools-v6#1322 (comment))

However, I think that adding this extra sanity check is reasonable since relying on globally available methods like this is always at the risk of failure, causing console spam

[posva]

Thanks!