Fix handling of empty 'types', 'typings', etc. fields in package.json

[rbuckton]

According to the documentation for Node's module resolution:

LOAD_AS_DIRECTORY(X)
1. If X/package.json is a file,
   a. Parse X/package.json, and look for "main" field.
   b. If "main" is a falsy value, GOTO 2.
   c. let M = X + (json main field)
   d. LOAD_AS_FILE(M)
   e. LOAD_INDEX(M)
   f. LOAD_INDEX(X) DEPRECATED
   g. THROW "not found"
2. LOAD_INDEX(X)

Step 1.b. indicates we should ignore a "falsy" value for "main", and we should probably do the same for "types", however in both cases we only check for undefined and allow "". This PR changes our behavior to align with NodeJS and ignore "".

Fixes #28304