Fix scripts for npm by extracting run command out

[gosar]

Currently, for npm the concurrently syntax was concurrently 'npm run-script:build:cjs' which is wrong and didn't work. npm:build:cjs (similar to yarn:build:cjs) is good syntax for concurrently.

Extracting run-script out of PackageManager.getCommand and specifying run directly in package.json scripts (prepack). run is equivalent alias to run-script in npm.

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[trivikr]

What's the issue with npm:?
https://github.com/open-cli-tools/concurrently#usage

[gosar]

What's the issue with npm:? https://github.com/open-cli-tools/concurrently#usage

concurrently 'npm:build:cjs' would have worked, but https://github.com/awslabs/smithy-typescript/blob/d02ff5910ec9e23ee4344b6fcb50a66784b36e2e/smithy-typescript-codegen/src/main/java/software/amazon/smithy/typescript/codegen/TypeScriptSettings.java#L398 is npm run-script which works for other parts like https://github.com/awslabs/smithy-typescript/blob/d02ff5910ec9e23ee4344b6fcb50a66784b36e2e/smithy-typescript-codegen/src/main/resources/software/amazon/smithy/typescript/codegen/base-package.json#L13

Could be refactored, but seems this syntax is also fine, maybe clearer.

[trivikr]

This is incorrect as npm run-script is not a packageManager
https://github.com/awslabs/smithy-typescript/blob/d02ff5910ec9e23ee4344b6fcb50a66784b36e2e/smithy-typescript-codegen/src/main/java/software/amazon/smithy/typescript/codegen/TypeScriptSettings.java#L396-L398

We should create a new method on PackageManager, say getRunCommand which returns empty string ("") for yarn and "run script" for npm.

The prepack script can be changed to:

"prepack": "${packageManager} ${pmRunCommand} clean && ${packageManager} ${pmRunCommand} build"

and PackageJsonGenerator can contain the additional line:

template = template.replace("${pmRunCommand}", settings.getPackageManager().getRunCommand());