[TS] Fix relative paths for exports (#8517)

Fixes an issue where exports were using incorrect relative paths for
>=3 namespace levels. This is fixed by making the starting range of the
namespace components relative to the amount of components.

Co-authored-by: Björn Harrtell <bjornharrtell@users.noreply.github.com>

tests/ts/longer-namespace/a/b/c/person.js

@@ -0,0 +1,54 @@
+// automatically generated by the FlatBuffers compiler, do not modify
+/* eslint-disable @typescript-eslint/no-unused-vars, @typescript-eslint/no-explicit-any, @typescript-eslint/no-non-null-assertion */
+import * as flatbuffers from 'flatbuffers';
+export class Person {
+    constructor() {
+        this.bb = null;
+        this.bb_pos = 0;
+    }
+    __init(i, bb) {
+        this.bb_pos = i;
+        this.bb = bb;
+        return this;
+    }
+    static getRootAsPerson(bb, obj) {
+        return (obj || new Person()).__init(bb.readInt32(bb.position()) + bb.position(), bb);
+    }
+    static getSizePrefixedRootAsPerson(bb, obj) {
+        bb.setPosition(bb.position() + flatbuffers.SIZE_PREFIX_LENGTH);
+        return (obj || new Person()).__init(bb.readInt32(bb.position()) + bb.position(), bb);
+    }
+    name(optionalEncoding) {
+        const offset = this.bb.__offset(this.bb_pos, 4);
+        return offset ? this.bb.__string(this.bb_pos + offset, optionalEncoding) : null;
+    }
+    age() {
+        const offset = this.bb.__offset(this.bb_pos, 6);
+        return offset ? this.bb.readInt16(this.bb_pos + offset) : 0;
+    }
+    static startPerson(builder) {
+        builder.startObject(2);
+    }
+    static addName(builder, nameOffset) {
+        builder.addFieldOffset(0, nameOffset, 0);
+    }
+    static addAge(builder, age) {
+        builder.addFieldInt16(1, age, 0);
+    }
+    static endPerson(builder) {
+        const offset = builder.endObject();
+        return offset;
+    }
+    static finishPersonBuffer(builder, offset) {
+        builder.finish(offset);
+    }
+    static finishSizePrefixedPersonBuffer(builder, offset) {
+        builder.finish(offset, undefined, true);
+    }
+    static createPerson(builder, nameOffset, age) {
+        Person.startPerson(builder);
+        Person.addName(builder, nameOffset);
+        Person.addAge(builder, age);
+        return Person.endPerson(builder);
+    }
+}