Runtime API: Extend InvestmentPortfolio with pending swaps

[wischli]

Description

• Successor of Investments: RuntimeApi for redeem and collected tokens #1589
• In order to be complete, the InvestmentPortfolio API needs to be extended by pending token swaps

Proposal

struct InvestmentPortfolio {
    ...
    /// Investment currency locked and awaiting a swap to the pool currency to be invested
    pending_invest_swaps: BTreeMap<Currency, Balance>,
    /// Pool currency locked and awaiting a swap to the investment currency to be claimed
    pending_redeem_swaps: BTreeMap<Currency, Balance>,
}

For now, this design is a bit overkill as there can be at most one swap per (investment_id, account_id) pair such that at most one of the maps would have exactly one entry. However, in the future we want to open up multiple investments for the same (investment_id, account_id) pair (project name MultiCurrency) which will benefit from the above design.

Research/based on

Conversation in k-f slack with @hieronx: https://kflabs.slack.com/archives/C05JM3VBD9V/p1701342364508009?thread_ts=1701340658.313919&cid=C05JM3VBD9V

How will this affect the code base

Improves UX

What are foreseen obstacles or hurdles to overcome?

Bump InvestmentsApi from V1 to V2