tree: More schema cleanup

[CraigMacomber]

Description

Reduce use of SchemaBuilderInternal.

Fix missing sort when persisting field schema found while editing test schema: this is not a correctness issue, but should improve consistency and thus blob reuse in the encoded format.

Reviewer Guidance

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[CraigMacomber]

these tests are for a function, requireSchema, that is no longer in the file this file is testing. schematizingTreeView.spec.ts
is the proper place for these, and it has relatively good coverage already, so only one of these two tests was ported to it.

[msfluid-bot]

⯅ @fluid-example/bundle-size-tests: +259 Bytes

Metric Name	Baseline Size	Compare Size	Size Diff
aqueduct.js	459.99 KB	460.03 KB	⯅ +35 Bytes
azureClient.js	558.03 KB	558.07 KB	⯅ +49 Bytes
connectionState.js	680 Bytes	680 Bytes	■ No change
containerRuntime.js	260.81 KB	260.82 KB	⯅ +14 Bytes
fluidFramework.js	402.98 KB	403 KB	⯅ +21 Bytes
loader.js	134.26 KB	134.28 KB	⯅ +14 Bytes
map.js	42.3 KB	42.31 KB	⯅ +7 Bytes
matrix.js	146.47 KB	146.48 KB	⯅ +7 Bytes
odspClient.js	525.31 KB	525.36 KB	⯅ +49 Bytes
odspDriver.js	97.72 KB	97.74 KB	⯅ +21 Bytes
odspPrefetchSnapshot.js	42.78 KB	42.79 KB	⯅ +14 Bytes
sharedString.js	163.18 KB	163.18 KB	⯅ +7 Bytes
sharedTree.js	393.49 KB	393.5 KB	⯅ +14 Bytes
Total Size	3.3 MB	3.3 MB	⯅ +259 Bytes

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Baseline commit: c3f64a9

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