continue #199: redesign the bundled file structure

According to @eoghanmurray's suggestion, we can support three
main scenarios:
1. record only
2. replay only
3. all in one

Since we have implemented the packer feature, which has a big
influence in bundle size, we provide another three bundles:
1. record and pack
2. replay and unpack
3. all in one with pack and unpack

src/entries/all.ts

@@ -0,0 +1,2 @@
+export * from '../index';
+export * from '../packer';

src/entries/record-pack.ts

@@ -0,0 +1,2 @@
+export * from '../record/index';
+export * from '../packer/pack';

src/entries/replay-unpack.ts

@@ -0,0 +1,2 @@
+export * from '../replay';
+export * from '../packer/unpack';