feat(sdk-server-common): add support for custom base uris in FDv2 datasources

[joker23]

This will update from a pinned version to follow the v3 release branch

[github-actions]

@launchdarkly/js-sdk-common size report
This is the brotli compressed size of the ESM build.
Compressed size: 26360 bytes
Compressed size limit: 29000
Uncompressed size: 129188 bytes

[github-actions]

@launchdarkly/js-client-sdk size report
This is the brotli compressed size of the ESM build.
Compressed size: 32077 bytes
Compressed size limit: 34000
Uncompressed size: 114525 bytes

[github-actions]

@launchdarkly/js-client-sdk-common size report
This is the brotli compressed size of the ESM build.
Compressed size: 39108 bytes
Compressed size limit: 39300
Uncompressed size: 213642 bytes

[github-actions]

@launchdarkly/browser size report
This is the brotli compressed size of the ESM build.
Compressed size: 179691 bytes
Compressed size limit: 200000
Uncompressed size: 831704 bytes

[joker23]

Looks like the scope of this change is a bit bigger. We should support uri customization.