improve error handling of fetchBaseQuery

[phryneas]

Fixes #1234

It will still cause an error, but a graceful one without information to be lost. This is probably the best way to tackle that.

Also I added handling for "fetch" failing, e.g. due to connection loss.

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[github-actions]

size-limit report 📦

Path	Size
1. entry point: @reduxjs/toolkit (cjs.production.min.js)	12.2 KB (0%)
1. entry point: @reduxjs/toolkit (esm.js)	10.23 KB (0%)
1. entry point: @reduxjs/toolkit/query (cjs.production.min.js)	20.31 KB (+0.76% 🔺)
1. entry point: @reduxjs/toolkit/query (esm.js)	17.36 KB (+0.95% 🔺)
1. entry point: @reduxjs/toolkit/query/react (cjs.production.min.js)	22.11 KB (+0.73% 🔺)
1. entry point: @reduxjs/toolkit/query/react (esm.js)	19.74 KB (+1.25% 🔺)
2. entry point: @reduxjs/toolkit (without dependencies) (cjs.production.min.js)	5.54 KB (0%)
2. entry point: @reduxjs/toolkit (without dependencies) (esm.js)	5.52 KB (0%)
2. entry point: @reduxjs/toolkit/query (without dependencies) (cjs.production.min.js)	9.2 KB (+1.66% 🔺)
2. entry point: @reduxjs/toolkit/query (without dependencies) (esm.js)	9.58 KB (+1.74% 🔺)
2. entry point: @reduxjs/toolkit/query/react (without dependencies) (cjs.production.min.js)	2.27 KB (0%)
2. entry point: @reduxjs/toolkit/query/react (without dependencies) (esm.js)	2.12 KB (0%)
3. createSlice (esm.js)	5.16 KB (0%)
3. createEntityAdapter (esm.js)	5.2 KB (0%)
3. configureStore (esm.js)	5.21 KB (0%)
3. createApi (esm.js)	15.64 KB (0%)
3. createApi (react) (esm.js)	17.96 KB (0%)
3. fetchBaseQuery (esm.js)	10.92 KB (+1.56% 🔺)
3. setupListeners (esm.js)	9.79 KB (0%)
3. ApiProvider (esm.js)	16.93 KB (0%)

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Vanilla Typescript	Configuration
funny-murdock-4slug	Issue #1234

[msutkowski]

I think this looks great 💪 . We'll just need to update docs to reflect these changes, but that's not a blocker for getting this in.