improvement(fetch-tool): Cache tokens in memory

[Abe27342]

Description

Adds in-memory caches for tokens and AuthenticationRecords. The former works around the problem described here, and the latter makes fetch-tool behave well when used with multiple accounts (which is mostly only a scenario for FF developers using it on stress or e2e test documents).

[msfluid-bot]

⯅ @fluid-example/bundle-size-tests: +245 Bytes

Metric Name	Baseline Size	Compare Size	Size Diff
aqueduct.js	460.47 KB	460.5 KB	⯅ +35 Bytes
azureClient.js	557.45 KB	557.5 KB	⯅ +49 Bytes
connectionState.js	724 Bytes	724 Bytes	■ No change
containerRuntime.js	259.74 KB	259.76 KB	⯅ +14 Bytes
fluidFramework.js	405.91 KB	405.92 KB	⯅ +14 Bytes
loader.js	134.34 KB	134.36 KB	⯅ +14 Bytes
map.js	42.46 KB	42.46 KB	⯅ +7 Bytes
matrix.js	148.63 KB	148.64 KB	⯅ +7 Bytes
odspClient.js	524.41 KB	524.46 KB	⯅ +49 Bytes
odspDriver.js	97.84 KB	97.86 KB	⯅ +21 Bytes
odspPrefetchSnapshot.js	42.81 KB	42.82 KB	⯅ +14 Bytes
sharedString.js	164.82 KB	164.83 KB	⯅ +7 Bytes
sharedTree.js	396.37 KB	396.38 KB	⯅ +7 Bytes
Total Size	3.31 MB	3.31 MB	⯅ +245 Bytes

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Baseline commit: 09d786a

Generated by 🚫 dangerJS against ef72056