Add onMutate to MutationCache

[stefanprobst]

following up on #3035 this pr allows adding a onMutate callback to the global MutationCache. this enables e.g. managing toast notifications for mutations in one central place (see example below). note that it is not allowed to return a context value from the onMutate callback.

example:

import { MutationCache, QueryClient, QueryClientProvider } from "react-query";
import { Toaster, toast } from "react-hot-toast";
import { useState } from "react";

export default function App({ Component, pageProps }) {
  const [client] = useState(() => {
    return new QueryClient({
      mutationCache: new MutationCache({
        onMutate(variables, mutation) {
          toast.loading("Submitting...", { id: mutation.mutationId });
        },
        onSuccess(data, variables, context, mutation) {
          toast.success("Success", { id: mutation.mutationId });
        },
        onError(error, variables, context, mutation) {
          toast.error("Failed", { id: mutation.mutationId });
        },
      }),
    });
  });

  return (
    <QueryClientProvider client={client}>
      <Component {...pageProps} />
      <Toaster />
    </QueryClientProvider>
  );
}

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[codecov]

Codecov Report

Merging #3038 (8182702) into master (dc2df10) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #3038   +/-   ##
=======================================
  Coverage   96.45%   96.45%           
=======================================
  Files          45       45           
  Lines        2257     2259    +2     
  Branches      641      641           
=======================================
+ Hits         2177     2179    +2     
  Misses         77       77           
  Partials        3        3           

Impacted Files	Coverage Δ
src/core/mutationCache.ts	100.00% <ø> (ø)
src/core/mutation.ts	100.00% <100.00%> (ø)

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[tannerlinsley]

🎉 This PR is included in version 3.34.0 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

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