internal/postgres: insert new_symbol_history
internal/postgres: insert new_symbol_history

Data is now inserted into the new_symbol_history table.

It is skipped for the existing symbol_history table when
ExperimentSkipInsertSymbols is active.

Change-Id: Ib38a86d52b1e919a267a4abf39d0e253055bb018
Reviewed-on: https://go-review.googlesource.com/c/pkgsite/+/324809
Trust: Julie Qiu <8d32267b6b4884cf35adeaccde2b6857ae11aace@golang.org>
Run-TryBot: Julie Qiu <8d32267b6b4884cf35adeaccde2b6857ae11aace@golang.org>
TryBot-Result: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>
Reviewed-by: Jonathan Amsterdam <e3d3698b2ccd5955e4adf250d0785062d0f9018b@google.com>

golang/pkgsite,golang/pkgsite,golang/pkgsite,golang/pkgsite